Use the following information to answer $2$a~$2$c:Treasury Bills, $90$ days$3\mathrm{.}00\%$Commercial Paper, $90$ days$3\mathrm{.}84\%$Treasury Bill, $1$ year$3\mathrm{.}67\%$Treasury Note, $2$ year$4\mathrm{.}25\%$Corporate Bond AA$,20$ year$7\mathrm{.}23\%$Municipal Bond AA$,20$ year$5\mathrm{.}42\%$Expected Annual Inflation Rate$3\mathrm{.}00\%$

$2$a$.$ Use the information above, how much is the default risk premium on the $90-$day commercial paper?

$2$b$.$ Use the information above, how much is the expected rate on the one$-$year Treasury in year $2?$

$2$c$.$ Use the information above, at what marginal tax rate would an investor be indifferent between owning the corporate bond and the municipal bond?