a zookeeper needs to create a diet containing a minimum of 20 grams of fat, 40 grams of carbohydrates, and 5 grams of protein. The tigers should be fed no more than 20 grams of food at each meal. To cut costs, it is cheaper to order Feed X and Feed Y and mix them for food. Feed X contains 7 grams of fat while Feed Y contains 4 grams of fat. Feed X contains 5 grams of carbohydrates while Feed Y contains 8 grams of carbohydrates . Feed X contains 11 grams of protein while Feed Y contains 4 grams of protein. Feed X costs $0.80 per ounce while Feed Y costs $0.65 per ounce. How much many ounces of Feed X should to zoo buy to minimize total cost?