For a weak acid $HA$ with $Ka=1\mathrm{.}0{10}^{-5},$ if the initial concentration of $HA$ is $0\mathrm{.}1M$ and the equilibrium concentration of $A-$ is $0\mathrm{.}02M,$ what is the $pH$ of the solution?

$4\mathrm{.}7$

$5\mathrm{.}0$

$5\mathrm{.}3$

$5\mathrm{.}7$