A stock's average return is $15$ percent. The average risk$-$free rate is $4$ percent. The standard deviation of the stock's return is $20$ percent, and the stock's beta is $1\mathrm{.}4.$ What is the Treynor Index for the stock?

$\mathrm{.}079$

$\mathrm{.}75$

$1\mathrm{.}33$

$\mathrm{.}02$

$\mathrm{.}50$