Two girder designs are under consideration for a bridge for a 1,200-foot crossing. The first design is expected to result in a superstructure weight per foot of 22(S) + 800, where S is the span between piers. The second design should result in superstructure weight per foot of 20(S) + 1,000. Piers and two required abutments are estimated to cost $220,000 each. Let X = the number of piers plus abutments. The superstructure will be erected at a cost of $0.55 per pound. Choose the girder design that will result in a minimum cost and specify the optimum value for X. Hint: X must be an integer.