Timperly Industries manufactures screens for residential (doors and windows) and commercial (chemical filters) applications. The firm is trying to strengthen its formal budgeting and planning process. It has encountered a problem in budgeting utilities expense. The expense is apparently a mixed cost and varies most directly with machine hours worked. However, management does not know the exact relationship between machine hours and utilities expense. The following data have been gathered from recent operations and may serve as a basis to describe the relationship.