What is the appropriate risk$-$free rate on Apr $26,2024$ for an option that expires on Dec $16,2024$ if the T$-$bill with closest maturity is quoted as $4\mathrm{.}6/4\mathrm{.}24?$

a$.$ What is the un$-$annualized discount rate?

b$.$ What is the T$-$bill price?

b$.$ What is the approximate risk$-$free rate?