An investor is considering purchasing a bond with a $4\mathrm{.}25$ percent coupon interest rate, a par value of $$1,000,$ and a market price of $$848\mathrm{.}44.$ The bond will mature in nine years. Based on this information, answer the following questions:

a$.$ What is the bond's current yield?

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

c$.$ What is the bond's yield to maturity using a financial calculator?