Please solve A$,$ B

Suppose the two most important macroeconomic sources of risk are the state of the business cycle reflected in returns on a market index and unanticipated changes in interest rates captured by returns on a Treasury$-$bond portfolio. Northwest Airlines has a market beta of $1\mathrm{.}2$ and T$-$bond beta of $0\mathrm{.}7.$

A$.$ Write down the mathematical expression of the two$-$factor security market line for the security of Northwest Airlines.

B$.$ Suppose the risk premium of the market index is $6\%,$ while that of the T$-$bond portfolio is $3\%$ and the risk$-$free rate is $4\%.$ What is the total risk premium of the Northwest Airlines stock? What is the total expected return of the Northwest Airlines stock?