An animal breeder can buy four types of food for vietnamese pot-bellied pigs. each case of brand a contains 25 units of fiber, 40 units of protein, and 40 units of fat. each case of brand b contains 100 units of fiber, 130 units of protein, and 120 units of fat. each case of brand c contains 275 units of fiber, 350 units of protein, and 340 units of fat. each case of brand d contains 200 units of fiber, 260 units of protein, and 220 units of fat. how many cases of each brand should the breeder mix together to obtain a food that provides 3975 units of fiber, 5100 units of protein, and 4860 units of fat? let x represent the number of cases of brand a, y represent the number of cases of brand b, z represent the number of cases of brand c, and w represent be the number of cases of brand d. there are four ways in which the breeder can mix brands to obtain a food that provides 3975 units of fiber, 5100 units of protein, and 4860 units of fat.