Sasha buys a warm soda and a slice of cold pizza. The marginal utility from a soda is 40, and the price of the soda is $1. The marginal utility from a slice of pizza is 80. Since Sasha always chooses the utility-maximizing choice, we know the price of a slice of pizza must be:
A) $0.50.
B) $1.
C) $20.
D) $2.