Cost of capital is: the coupon rate of debt. a hurdle rate set by the board of directors. the average cost of the firm's assets. the rate of return that must be earned on additional investment if firm value is to remain unchanged. Cost of capital is commonly used interchangeably with all of the following terms except: the firm's required rate of return. the internal rate of return for new investments. the hurdle rate for new investments. the firm's opportunity cost of funds