A company prepares a budget each month for manufacturing costs. Formulas have been
developed for all costs within a relevant range of 5,000 to 15,000 units per month. The
budget for electricity (a semi variable cost) is $19,800 at 9,000 units per month, and $21,000
at 10,000 units per month. How much should be budgeted for electricity for the coming
month if 12,000 units are to be produced?