$4.$ The Tyler Energy Corporation's $$1,000$ par bonds currently sell for $$940,$ mature in seven years, and have semiannual coupon payments with a $8\mathrm{.}2\%$ annual coupon rate.

a$.$ What is the current yield?

b$.$ What is the yield to maturity $($to the nearest basis point$)$

c$.$ What is the horizon yield for an investor with a $4-$year holding period and a reinvestment rate of $6\mathrm{.}8\%$ over the period. At the end of the four years, the bonds will sell to yield $8\mathrm{.}2\%.$ Please do it on excel.