Solve the Problem $M ( x )$ , in Millions, in a Certain Area Depends on the )

Multiple Choice

Solve the problem.
-The number of mosquitoes $M ( x )$ , in millions, in a certain area depends on the June rainfall $x$ , in inches, according to the equation $M ( x ) = 6 x - x ^ { 2 }$ . What rainfall produces the maximum number of mosquitoes?

A) 3 in.
B) $6 \mathrm { in. }$
C) $0 \mathrm { in }$ .
D) $36 \mathrm { in. }$