$5-$year Treasury bonds yield $6\mathrm{.}90\%.$ The inflation premium $($IP$)$ is $1\mathrm{.}50\%,$ and the maturity risk premium $($MRP$)$ on $5-$year bonds is $0\mathrm{.}6\%.$ What is the real risk$-$free rate, r$*?$

a$.6\mathrm{.}21\%$

b$.4\mathrm{.}80\%$

c$.4\mathrm{.}73\%$

d$.5\mathrm{.}40\%$

e$.6\mathrm{.}30\%$