Consider the regression equation: r_it - r_ft = a_i + b_i(r_mt - r_ft) + e_it where: r_it = return on stock i in month t r_ft = the monthly risk-free rate of return in month t r_mt = the return on the market portfolio proxy in month t This regression equation is used to estimate

benchmark error

b.

the security characteristic line

c.

None of the options

d.

All of the options

e.

the capital market line