Multiply 0.45 (the cost of making 3 donuts) by 4 to find the cost of making a dozen donuts: 0.45 × 4 = 1.80. Then multiply the cost of making a dozen donuts by 5 to determine the cost per 5 dozen: 1.80 × 5 = 9.00. Next, multiply the selling price per dozen times 5, the number of dozens sold: 3.99 × 5 = 19.95. Finally subtract the cost of making 5-dozen donuts from the price the baker sells them for to determine the profit: 19.95 – 9.00 = 10.95.