A staff person has been asked to prepare a diet for ferrets. The diet is limited to two brands of food, brand A and brand B. The total amount of food in the diet should be no larger than 8 ounces and must contain at least 26 units of protein and 18 units of carbohydrates. Each ounce of brand A contains 5 units of protein and 3 units of carbohydrates. Each ounce of brand B contains 5 units of protein and 2 units of carbohydrates. The cost of brand A is 4 per ounce and for brand B the cost is 4 per ounce. How many ounces of each brand of food should be used to meet the given requirements at the lowest possible cost