An Open Box of Maximum Volume Is to Be Made

An open box of maximum volume is to be made from a square piece of material 30 centimeters on a side by cutting equal squares from the corners and turning up the sides(see figure) . What is the domain of the function V = x(30 - 2x) ². ​ ​

A) domain: 0 < x < ∞
B) domain: 30
C) domain: 0 < x < 15
D) domain: 0 < x < 30
E) domain: 15