An animal feed producer mixes two types of grain: x and y. each unit of grain x contains 20 grams of fat, 10 grams of protein, and 800 calories, each unit of grain y contains 30 grams of protein, 30 grams of fat, and 600 calories. suppose that the producer wants each unit of the final product to yeild at least 180 grams of fat, 120 grams of protein, and 4,800 calories. if each unit of x costs 180 (pesos) and each unit of y costs 160 (pesos). how many units of each type of grain should the producer use to minimize his cost?