Alright, so now let's put together the ideas of the budget constraint and our indifference curves to find the consumer's optimum consumption. So the consumer's optimum consumption, this is going to be where the consumer gets the maximum amount of utility, right? They want to get as much satisfaction, as much utility within their budget, right? They're only going to have so much money to get as much utility as possible out of it, okay? So when we talk about optimum consumption with indifference curves and budget constraints, okay? So okay. So tangent, it's this mathematical concept and that's where they touch only they touch only at one point. At one point. Okay? So they only touch at one point. You're going to have an indifference curve and a budget constraint that they just touch at one point and that's going to be that optimum consumption right where they touch. Okay?

So let's go back to our example of party boy Paul and wrap this all up together in 1. So, party boy Paul, we're going back to a situation where his income was $24, vodka was selling for $6 and beer was selling for $3. Alright. So, we've got an income of 24, vodka selling for $6 and beer selling for $3. Okay? And what we did is we had found out previously, we had graphed his utility curve or his indifference curves right for levels of 500 utility right here and 750 utility out here. Right? And then what we also have is his budget constraint, which we also figured out to be this line right here is going to be his budget constraint. Okay. So, we've got it all on one graph now. So, it should be pretty easy for you at this point to pick out what his optimum consumption is going to be based on his constraint of his budget. Well, it's going to be right here at the tangent, right? This is the only point where this utility curve touches the budget constraint, okay, and that is going to be the optimum consumption because we're getting the most utility, we're on the furthest out utility curve that is affordable in our budget. Of course, party boy Paul would prefer this other curve, right? He would prefer to be on this 750 utility curve, there's more satisfaction there, but he can't afford it. No part of his budget touches that 750 utility curve, so it is not affordable for him. None of those options are affordable, but what about a situation like this? If I were to draw another curve down here, what about this curve that I just drew? It crosses his budget constraint right there, doesn't it? But this is going to have less utility, right? Because it's closer to the origin, it's lower than the 500 utility point, so this isn't his ideal situation right? He would say in this case maybe he's only getting 250 utility from this graph, right? So he doesn't want to be on that curve. He wants to be on the furthest out curve with the most satisfaction and that's going to be the 500 utility curve right there where they're tangent, okay? So, that is going to be his optimum consumption where the indifference curve touches the budget constraint. Alright?

So let's real quick, let's see how a change in income or a change in the price of a good can affect our optimum consumption. Alright? So, we've seen how the change in income or change in price of good, how that affects our budget constraint, right? And what's going to happen is since we have a different budget constraint, we're going to have a different optimum consumption. So let's see this first example where we're going to have a change in income. Let's say, party boy Paul makes even more money now and his income increases. What we saw when there's an increase in income, he's going to shift outward, right? We're going to see that the line shifts outward and he might be in a situation something like I don't know. Let's go I wanted to touch this curve. So, I'm gonna do something like this. Too far. Let me There you go. Something like that would be his new budget constraint. Now I didn't draw it perfect cause it should be parallel to the other one, but the idea is that it's moved out, right, because he's making more money. I'll try it one more time. I don't like how that looked. So, let's try one more here. Okay, let's say that that touched, that was almost parallel, so you could imagine it's almost touching there and this could be that point, right? That would be the point of his new optimum consumption, where his previous optimum consumption was somewhere around there, right? So, we moved our income, so we can move to a new utility curve and you could imagine if we had a decrease in income, if we had something like this where our income went down here, well, we would have to find a new utility curve down here that's touching, excuse me, new indifference curve that's touching our lower income, right. So the whole key there is just to find the utility curve that is just touching the budget constraint at one point, right, and remember that these 2 are not all of our indifference curves. There's indifference curves in between here. There's all indifference curves for different levels of utility everywhere. Every little marginal bit of utility, there can be more, more indifference curves there. Okay, so even if it wasn't touching one of these, we could find a new utility curve that it was touching. Alright, so that is how the change in income can affect it, right? We shifted our income out and we ended up on a different utility curve. Now what about the change in the price of a good? Let's say now the price of vodka goes down and we can afford way more vodka. Well remember what's going to happen is that the vodka side is going to change, but the beer stays constant, right? The price of the beer is the same, the income's the same, so that's not gonna move, but the vodka side will move and since we can afford more, it's gonna move out this way. Okay? So we might end up in a situation where a new budget constraint might look something like this, Right? Where we still have the same point down here, but now we've got a new point up here and we have our new optimum quantity somewhere around there where it's just touching and it's tangent just at one point. So this is the new optimum on both graphs. New optimum. Okay, so the shifting of the budget constraint leads us to move to a different indifference curve or to a different point, right? So we just got to find where we're going to have that tangency condition and that will be our optimum consumption. Cool? Alright. Let's go ahead and move on to the next video.