Solve the Problem
-The Number of Mosquitoes $\mathrm { M } ( \mathrm { x } )$

Multiple Choice

Solve the problem
-The number of mosquitoes $\mathrm { M } ( \mathrm { x } )$ , in millions, in a certain area depends on the June rainfall $\mathrm { x }$ , in inches, according to the equation $\mathrm { M } ( \mathrm { x } ) = 9 \mathrm { x } - \mathrm { x } ^ { 2 }$ . What rainfall produces the maximum number of mosquitoes?

A) $0 \mathrm { in }$ .
B) $9 \mathrm { in }$ .
C) $4.5 \mathrm { in }$ .
D) $81 \mathrm { in }$ .