Jackson's Auto Body Calculates That Its Total Fixed Costs Are

Jackson's Auto Body calculates that its total fixed costs are $3,000 per month. In a month in which the company repairs 20 cars, it finds that its total costs are $12,000. From this,we can conclude

A) total monthly cost is $15,000
B) marginal cost is $600
C) average fixed cost is $60
D) average variable cost is $450
E) the costs are too high so the company should shut down