A special low-calorie diet consists of dishes a, b and
c. each unit of a has 2 grams of fat, 1 gram of carbohydrate and 3 grams of protein. each unit of b has 1 gram of fat, 2 grams of carbohydrate and 1 gram of protein. each unit of c has 1 gram of fat, 2 grams of carbohydrate and 3 grams of protein. the diet must provide exactly 10 grams of fat, 14 grams of carbohydrate and 18 grams of protein. how much of each dish should be used?