A small bakery makes a profit $P(c)$ in dollars from selling $c$ cakes per day according to the formula $P(c) = c(40 - c) - 80$. Considering that $P$ is a continuous function, how many cakes should the bakery sell per day to maximize its profit?

• A. The bakery should sell $10$ cakes per day to maximize its profit.
• B. The bakery should sell $20$ cakes per day to maximize its profit.
• C. The bakery should sell $30$ cakes per day to maximize its profit.
• D. The bakery should sell $40$ cakes per day to maximize its profit.

Answer: (B)