Problem $10-32($Algo$)$

A $20-$year maturity, $7\mathrm{.}9\%$ coupon bond paying coupons semiannually is callable in seven years at a call price of $$1,155.$ The bond currently sells at a yield to maturity of $6\mathrm{.}9\%(3\mathrm{.}45\%$ per half$-$year$).$

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Required:

a$.$ What is the yield to call? $($Do not round intermediate calculations. Round your answer to $2$ decimal places.$)$

b$.$ What is the yield to call if the call price is $$1,155$ but the bond can be called in four years instead of seven years? $($Do not round intermediate calculations. Round your answer to $2$ decimal places.$)$