cost $$5$ per system. A supervisor was hired to oversee production; her monthly salary is $$4,000.$

Factory janitorial costs are $$1,820$ monthly. Advertising costs for the audio system will be $$9,230$ per month. The factory building depreciation is $$6,360$ per year. Property taxes on the factory building will be $$9,480$ per year.

$($a$)$