Suppose you need to minimize the cost of fencing in a rectangular region with a total area of 500 square feet. The material that will be used for three sides costs $15 per linear foot, and the material that will be used for the fourth side costs $27 per linear foot. Write a function that expresses the cost of fencing the region in terms of the length, x, of the two opposite sides of the region with material costs of $15 per linear foot.