Solve the Problem $$P ( x ) = - 0.002 x ^ { 2 } + 1.6 x - 350$$

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