a-1. Use the high-low method to determine the variable element of manufacturing overhead costs per machine-hour. a-2. Use the high-low method to determine the fixed element of monthly overhead cost. b. Bursa expects machine-hours in May to equal 4,500. Use the cost relationships determined in part a to forecast May's manufacturing overhead costs. c. Suppose Bursa had used the cost relationships determined in part a to estimate the total manufacturing overhead expected for the months of February and March. By what amounts would Bursa have over- or underestimated these costs