Solve the Problem
-The Profit That the Vendor Makes Per $x$

Multiple Choice

Solve the problem
-The profit that the vendor makes per day by selling $x$ pretzels is given by the function $P ( x ) = - 0.004 x ^ { 2 } + 2.4 x - 400$ . Find the number of pretzels that must be sold to maximize profit.

A) 600 pretzels
B) $1.2$ pretzels
C) 300 pretzels
D) $- 40$ pretzels