Diddy Corporation stock has a beta of $1\mathrm{.}0,$ the current risk$-$free rate is $5$ percent, and the expected return on the market is $15\mathrm{.}5$ percent. What is Diddy's cost of equity?

Multiple Choice

$14\mathrm{.}20$ percent

$18\mathrm{.}50$ percent

$15\mathrm{.}50$ percent

$16\mathrm{.}30$ percent