A rectangular area adjacent to a river is to be fenced in; no fence is needed on the river side. The enclosed area is to be 1000 square feet. Fencing for the side parallel to the river is $5 per linear foot, and fencing for the other two sides is $8 per linear foot; the four corner posts are $25 apiece. Let x be the length of one of the sides perpendicular to the river.

(a) Write a function C((x) that describes the cost of the project.

(b) What is the domain of C?

(c) Use a graphing utility to graph C = C(x).

(d) Find the dimensions of the cheapest enclosure.