Question

Food A ha 560 calories per pound and 80 units of vitamins per pound, food B has 240 calories per pound and 400 units of vitamins per pound, and food C has 480 calories per pound and 160 units of vitamins per pound. It is desired to have a 5-lb mixture of foods A, B and C to contain a total of 2000 calories and 1200 units of vitamins. If x pounds of A, y pounds of B, and z pounds of C are to be used to make up the 5 lb, what are the restrictions on x, y, and z