please include excel formulas and example

Twin Oaks Health Center has a bond issue outstanding with a coupon rate of 7 percent and four years remaining until maturity. The par value of the bond is $1,000, and the bond pays interest annually. a. Determine the current value of the bond if present market conditions justify a 12 percent required rate of return. b. Now, suppose Twin Oaks' four-year bond had semiannual coupon payments. What would be its current value? (Assume a 6 percent semiannual required rate of return. However, the actual rate would be slightly less than 6 percent because a semiannual bond is slightly less risky than an annual coupon bond.) c. Assume that Twin Oaks' bond had a semiannual coupon but 20 years remaining to maturity. What is the current value under these conditions? (Again, assume a 6 percent semiannual required rate of return, although the actual rate would probably be greater than 6 percent because of increased price risk.)