A dog owner decides to feed his pet Doberman pinscher a combination of two dog foods. Each can of brand A contains 3 units of protein, 1 unit of carbohydrates, and 2 units of fat and costs $2.30. Each can of brand B contains 1 unit of protein, 1 unit of carbohydrates, and 6 units of fat and costs $1.80. He feels that, each day, his dog should have at least 6 units of protein, 4 units of carbohydrates, and 12 units of fat. How many cans of each dog food should he give to his dog each day to provide the minimum requirements at the least cost?