15. The manufacturing costs of Ackerman Industries for the first three months of the year follow: Total Costs Units Produced January $1,900,000 20,000 units February 2,250,000 27,000 March 2,400,000 30,000 Using the high-low method, determine (a) the variable cost per unit and (b) the total fixed cost. Round all answers to the nearest whole dollar. a. Variable cost per unit $ b. Total fixed cost $