The nutritionist of CMU Hospital serves lunch consisting of two courses, A and B. Each unit of A has 8 grams of fat, 6 grams of carbohydrates and 18 grams of protein whereas each unit of B has 8 grams of fat, 4 grams of carbohydrates and 26 grams of protein. If the nutritionist wants to provide the patients no more than 40 grams of fat, no more than 28 grams of carbohydrates, how many units of A and B should be served to maximize the amount of protein?