Linear Programming: Minimizing Materials Cost. Beauty Company produces a cosmetic product in 60-gallon batches. The basic ingredients used are Material X, costing $7 per gallon, and Material Y. costing $17 per gallon. No more than eighteen gallons of X can be used, and at least fifteen gallons of Y must be used. How would the objective function (minimization of product cost) be expressed? (AICPA adapted