Solve the Problem $x$ Represent the Length of a Side of Each Such Square

Multiple Choice

Solve the problem.
-A rectangular piece of cardboard measuring 30 inches by 50 inches is to be made into a box with an open top by cutting equal size squares from each corner and folding up the sides. Let $x$ represent the length of a side of each such square. For what value of $x$ will the volume be a maximum? If necessary, round to 2 decimal places.

A) $20.6$ in.
B) $6.07 \mathrm { in }$ .
C) $25 \mathrm { in }$ .
D) $41.2$ in.