Shelby drives her scooter at a speed of $30$ miles per hour if it is not raining, and $20$ miles per hour if it is raining. Today she drove in the sun in the morning and in the rain in the evening, for a total of $16$ miles in $40$ minutes. How many minutes did she drive in the rain?
$\textbf{(A)}\ 18 \qquad \textbf{(B)}\ 21 \qquad \textbf{(C)}\ 24 \qquad \textbf{(D)}\ 27 \qquad \textbf{(E)}\ 30$
Let $x$ be the time it is not raining, and $y$ be the time it is raining, in hours.
We have the system: $30x+20y=16$ and $x+y=2/3$
Solving gives $x=\frac{4}{15}$ and $y=\frac{2}{5}$
We want $y$ in minutes, $\frac{2}{5} \cdot 60=24 \Rightarrow C$