A dance studio charges $ \$ 10$ per student for its morning class and $ \$ 15 $ per student for its evening class. Three times as many students attended the evening class as attended the morning class. If the dance studio earns $ \$ 2200$ on Friday, how many students attended the morning class ?

Question

$\begin{array}{1 1} (a)\; 20 \\ (b)\; 30 \\ (c)\; 40 \\ (d)\; 50 \end{array}$