A company manufactures clock-radios. The fixed cost of producing clock-radios is $ 500 , and the variable cost of producing a single clock radio is $ 9 . If x is the quantity of clocks produced, what is the cost function for the company? Select all that apply: C ( x ) = 509 x C ( x ) = 500 x + 9 C ( x ) = 500 + 9 x C ( x ) = 509 + x C ( x ) = 500 9 x