Budgeting Mercury Corporation incurs the following overhead costs to manufacture its product: Indirect materials $4 per unit Indirect labor $3 per unit Manager salaries $168,000 per month Deprec. of plant and equipment $116,000 per month Utilities $6,000 per month + $0.50 per unit Prepare a flexible overhead cost budget for the following production amounts: 12,000 units 16,000 units 20,000 units