The regular rate of full body massage at a spa clinic is $\$50$ per session. The clinic currently offers a special package of $\$240$ for 6 sessions. What percentage does a customer taking up this offer save for 6 sessions ?

Question

$\begin{array}{1 1} (a)\;5 \% \\ (b)\;10 \%\\ (c)\;15 \% \\(d)\;20 \% \end{array}$