The annual return on the S&P $500$ Index was $13\mathrm{.}4$ percent. The annual T$-$bill yield during the same period was $4\mathrm{.}7$ percent. What was the market risk premium during that year? a$)4\mathrm{.}7$ percent b$)8\mathrm{.}7$ percent c$)13\mathrm{.}4$ percent d$)18\mathrm{.}1$ percent