PROBLEM 3-15 High-Low Method; Predicting Cost [LO1, LO2] Prince Company's total overhead costs at various levels of activity are presented below: Assume that the overhead cost above consists of utilities, supervisory salaries, depreciation, and maintenance. The breakdown of these costs at the 80,000-machine-hour level of activity in October is as follows: The company wants to break down the maintenance cost into its variable and fixed cost elements. Required: 1. Estimate how much of the $483,200 of overhead cost in December was maintenance cost. (Hint: To do this, first determine how much of the $483,200 consisted of utilities and supervisory salaries. Think about the behaviour of variable and fixed costs within the relevant range.) 2. Using the high-low method, estimate a cost formula for maintenance. 3. Express the company's total overhead cost in the form Y=a+bX. 4. What total overhead cost would you expect to be incurred at an activity level of 90,000 machine-hours