HEALTH: Mike May has been told that each day he needs at least 16 units of Vitamin A, at least 5 units of Vitamin B-1, and at least 20 units of Vitamin C. Each Brand X pill contain 8 units of Vitamin A, 1 of vitamin B-1, and 2 of vitamin C, while each Brand Z pill contains 2 units of vitamin A, 1 of vitamin B-1,, and 7 of vitamin C. A Brand X pill costs 15 cents, and a Brand Z pill cost 30 cent. How many pill of each brand should he buy to minimize his daily cost? What is the minimum cost?