Wellspring produces agricultural irrigation equipment. During a year, the amount of overhead costs on a per month basis varies in relation to the machine hours used in a given year. The low for the past year was 4,500 hours, and the expense associated was $90,000. The high for the period was 6,000 hours, and the associated expense was $140,000. During the low month, the $90,000 in overhead costs consisted of indirect materials of $45,000 (a variable expense), rent of $35,000 (a fixed expense), and maintenance costs of $10,000 (a mixed expense).

Requirements
1. Given the breakdown of expenses in the low period, what are the estimated costs for

(a) Indirect materials,

(b) Rent, and

(c) Maintenance during the high period?

2. What is the cost function for maintenance costs?

3. What amount of maintenance costs would expect with 8,000 machine hours of work?

4. What would be the total overhead costs at 8,000 machine hours?