Bill and Joe each put $10$ into separate accounts at time, $t=0,$ where $t$ is measured in years.

Bill's account earns interest at a constant annual effective interest rate of $\frac{K}{25},K>0.$

Joe's account earns interest at a force of interest, ${}_t=\frac{1}{K+0\mathrm{.}25t}.$

At the end of four years, the amount in each account is $x.$

Calculate $x.$

$20\mathrm{.}7$

$21\mathrm{.}7$

$22\mathrm{.}7$

$23\mathrm{.}7$