If a person performing a task has been achieving a $75$ percent learning curve and you know that the task will end after the ${80}^{th}$ unit, the last unit produced will take percent as much time as the first unit.

$13\mathrm{.}71$

$14\mathrm{.}79$

$15\mathrm{.}45$

$16\mathrm{.}22$

$17\mathrm{.}12$