a manufacturer determines that the number of drills it can sell is given by the formula d=-3p^2+180p-285, where p is the price of the drills in dollars.
a. at what price will the manufacturer sell the maximum number of drills? (this is the x value of the vertex.)
b. what is the maximum number of drills that can be sold? (this is the y value of your vertex.)

a. $60; 285 drills

b. $90; 8,385 drills

c. $31; 2,418 drills

d. $30; 2,415 drills