Consider the two $($excess return$)$ index model regression results for A and $B$ :

$R_A=1\%+1\mathrm{.}3R_M$

$R-$square $=0\mathrm{.}602$

Residual standard deviation $=11\mathrm{.}2\%$

$R_B=-1\mathrm{.}5\%+0\mathrm{.}7R_M$

$R-$square $=0\mathrm{.}466$

Residual standard deviation $=9\mathrm{.}3\%$

Required:

a$.$ Which stock has more firm$-$specific risk?

b$.$ Which stock has greater market risk?

c$.$ For which stock does market movement explain a greater fraction of return variability?

d$.$ If $r_f$ were constant at $4\mathrm{.}6\%$ and the regression had been run using total rather than excess returns, what would have been the regression intercept for stock $A?$