A closed box with a square base is to have a volume of 50 cubic inches. The material for the top and bottom of the box cost 25 cents per square inch, and the materials for the sides cost 20 cents per square inch. Express the construction cost of the box as a function of the length of the base, x.

1) V = _____________________________________

2) h = ______________________________________

3) C = ______________________________________

4) C(x) = ____________________________________