In a salon, an average customer will wait $28$ minutes before spending $18$ minutes with the stylist. What is the percentage of value$-$added time?

Question $7$ options:

$74\mathrm{.}5\%$

$60\mathrm{.}9\%$

$48\mathrm{.}2\%$

$39\mathrm{.}1\%$