Nova Company's total overhead cost at various levels of activity are presented below: Total Month Machine-Hours Overhead Cost 70.00 60,000 80,000 90.000 $198,000 $174,000 $222,000 $246,000 April. May July Assume that the total overhead cost above consists of utilities, supervisory salaries, and main- tenance. The breakdown of these costs at the 60,000 machine-hour level of activity is: S48,000 21,000 105,000 $174,000 Maintenance (mixed) Nova Company's management wants to break down the maintenance cost into its variable and fixed cost elements. 1. Estimate how much of the $246,000 of overhead cost in July was maintenance cost. 2. Using the high-low method, estimate a cost formula for maintenance. 3. Express the company's total overhead cost in the linear equation Y- a+bX. 4. What total overhead cost would we expect to be incurred at an activity level of 75,00 machine-hours