PQR is a right angled triangle with PR = 3cm and QR = 4cm. The square STUV is inscribed in triangle PQR. What is the length, in centimeters of the side of the square.

A) 30/17

B) 12/7

C) 5/3

D) 60/37

E) 60/39

Please help!! and tell me how you did it..