What does the concept of diminishing marginal utility imply?

How does a consumer achieve optimum consumption?

If the price of Good A increases from \$2 to \$4, and the price of Good B remains at \$1, how should a consumer adjust their consumption bundle to maintain optimum consumption?

If the marginal utility of a good is 30 and its price is \$5, what is the marginal utility per dollar spent?

How does diminishing marginal utility affect consumer choices?

If the price of Good L is \$4 and its marginal utility is 32, what is the marginal utility per dollar spent?

If the price of Good C is \$3 and its marginal utility is 18, what is the marginal utility per dollar spent?