Solve
-The Profit That the Vendor Makes Per Day by Selling

Multiple Choice

Solve.
-The profit that the vendor makes per day by selling $x$ pretzels is given by the function $P ( x ) = - 0.002 x ^ { 2 } + 1.6 x - 150$ . Find the number of pretzels that must be sold to maximize profit.

A) 800 pretzels
B) 400 pretzels
C) $0.8$ pretzels
D) 170 pretzels