2013 Cayley Problem 19

In the diagram, PQ is parallel to RS. Also, Z is on PQ and X is on RS. If Y is located between PQ and RS so that \angle YXS = 20^\circ and \angle ZYX = 50^\circ, what is the measure of \angle QZY?

\textbf{(A)}\ 30^\circ\quad \textbf{(B)}\ 20^\circ\quad \textbf{(C)}\ 40^\circ\quad \textbf{(D)}\ 50^\circ\quad \textbf{(E)}\ 60^\circ

If there are no answer choices shown, enter a numerical answer.

Full credit to this problem is given to the CEMC, you may view all Cayley contests here.