A rancher is mixing two types of foods A and B. The cattle require 60 grams of protein and 30 grams of fat in each serving. Food A has 15 grams of protein and 10 grams of fat per unit. On the other hand, Food B has 20 grams of protein and 5 grams of fat. In terms of price, Food A cost 80 cents/unit and Food B costs 50 cents/unit. The rancher wants to minimize his cost. At the same time, he wants to make sure the cattle get required protein and fat. In this case, how much of each type of food should be used by the rancher?