Help? which one should I pick

Suppose that the price p (in dollars) and the weekly sales x (in thousands of units) of a certain commodity satisfy the demand equation 4p cubedplusx squaredequals38 comma 400. determine the rate at which sales are changing at a time when xequals80, pequals20, and the price is falling at the rate of $.20 per week.

15 and 14.7 are 1 apart, so 15 – 14.7 must be 1.

Ijust need these 2 questions answered (the second pic is just confirmation i'm not confident in that answer)