Each student needs 2/5 of cup of play dough to build a house how many cups of Play-Doh and waiting for nine students?

Hello people, i have a math question that i need with, me, i will give the correct one brainiest, and for the other correct people, a and 5 stars.

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.

A. 90 degrees b. 45 degrees c. 30 degrees d. 120 degrees