An agribusiness company mixes and sells chicken feed to farmers. The costs of the chicken feed ingredients vary throughout the chicken feeding season but the selling price of chicken feed is independent of ingredients. On August 1, management needs to know how many units of each of three grains (Q, R, and S) should be included in their chicken feed in order to produce the product most economically. The cost of each grain is, for unit of Q, $30; for a unit of R, $37; and for a unit of S, $78. Applying linear programming to this problem, which of the following is the objective function?
Minimize Z= 30Q+37R+78S