Dog foods to create a nutritious low-sodium diet. Each can of brand A contains 3 units of protein, 1 unit of calories, and 5 units of sodium. Each can of brand B contains 1 unit of protein, 1 unit of calories, and 4 units of sodium. Mr. Milan feels that each day, his dogs should have at least 12 units of protein and 8 units of calories. How many cans of each dog food should he give to both his dogs each day to provide the minimum requirements with the least amount of sodium? What is the least amount of sodium?