In the diagram, \triangle P Q R is right-angled at Q and point S is on P R so that Q S is perpendicular to P R. If the area of \triangle P Q R is 30 and P Q=5, the length of Q S is
Answer Choices
A. \frac{60}{13}
B. 5
C. \frac{30}{13}
D. 4
E. 3