The Wonder Drug Company's Total Overhead Costs at Various Levels

The Wonder Drug Company's total overhead costs at various levels of activity are presented below:
$$\begin{array} { l c c } & \text { Direct Lubor } \\\text { Month } & \text { Hours } & \text { Total Overhead } \\\text { Septernber } & 15,00 0& \$ 472,000 \\\text { October } & 12,00 0& 409,400 \\\text { Novernber } & 18,00 0& 542,000 \\\text { Decernber } & 21,000 & 604,700\end{array}$$
Assume that the overhead costs above consist of indirect labor, scheduling salaries, and maintenance. The breakdown of these costs for the month of November is as follows:
Indirect labor (V) $219,600
Maintenance (M) 197,400
Scheduling Salaries (F) 125,000
$542,000
Required:
(a.) Using the high-low method, determine the cost formula for maintenance.
(b.) Express the company's total overhead costs in linear equation form.