Medical Supply Company has a beta of $1\mathrm{.}55$ and recently paid a common stock dividend of $$3\mathrm{.}47.$ If the return on Treasury securities is currently $7\mathrm{.}5\%$ and the return on the S&P $500$ index is $12\%,$ what is the required rate of return on the firm's common stock?

a$)7\mathrm{.}5\%$

c$)18\mathrm{.}5\%$

e$)14\mathrm{.}48\%$

b$)26\mathrm{.}1\%$

d$)12\mathrm{.}93\%$