Strait Co. manufactures office furniture. During the most productive month of the year, 3,000 desks were manufactured at a total cost of $59,000. In the month of lowest production, the company made 1,125 desks at a cost of $38,000. Using the high-low method of cost estimation, total fixed costs are a.$21,000 b.$25,400 c.$42,000 d.$13,000