An investor buys a $20-$year Bbb$-$rated corporate bond with a nominal annual rate of return of $10\%.$ The average inflation rate is expected to be $2\%.$ The default risk premium is expected to be $5\%$ and the maturity premium is $4\%.$ Calculate the real rate of interest. use the formular below

krf $=$ k$*+$ IRP $+($k$*$ x IRP$)$ Solve for k$*$