Boeing Corporation has just issued a callable$($at par$)$ three$-$year, $4\mathrm{.}9\%$ coupon bond with$$ semi$-$annual coupon payments. The bond can be called at par in two years or anytime thereafter on a coupon payment date. It has a price of $$98\mathrm{.}73.$

a$.$ What is the$$ bond's yield to$$ maturity?

b$.$ What is its yield to$$ call?

c$.$ What is its yield to$$ worst?