Consider the following scenario.

A retailer uses a markup of $40\%$ based on selling price. She found that her competitor was using a markup of $30\%$ based on cost $.$ She wants to compare the markups.

Compute her $40\%$ markup on sellling as a markup percentage on cost$.$

$70\%$

$28\mathrm{.}6\%$

$66\mathrm{.}67\%$

$30\mathrm{.}8\%$