Solve the Problem $x$ Pretzels Is Given by the Function $P ( x ) = - 0.002 x ^ { 2 } + 1.6 x - 350$

Multiple Choice

Solve the problem.
-The profit that the vendor makes per day by selling $x$ pretzels is given by the function $P ( x ) = - 0.002 x ^ { 2 } + 1.6 x - 350$ . Find the number of pretzels that must be sold to maximize profit.

A) $0.8$ pretzels
B) $- 30$ pretzels
C) 800 pretzels
D) 400 pretzels