The Potomac Companys bonds have a face value of $1,000, will mature in 20 years, and carry a coupon rate of 8 percent. Assume interest payments are made semiannually. (a) Determine the present value of the bonds cash flows if the required rate of return is 15 percent. (b) Determine the present value of the bonds cash flows if the required rate of return is 18 percent. (c) Is there a change in the present value in the above two examples? If yes, give a reason.