A $30-$year maturity, $8\mathrm{.}3\%$ coupon bond paying coupons semiannually is callable in five years

at a call price of $$1,115.$ The bond currently sells at a yield to maturity of per

half$-$year$).$

$($a$)$ What is the yield to call?

$($b$)$ What is the yield to call if the call price is only $$1,065?$

$($c$)$ What is the yield to call if the call price is $$1,115$ but the bond can be called in two

years instead of five years?