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