Australian AMC 2008 - Intermediate Question 26

In the diagram, $\angle OPQ=\angle OQR=\angle ORS=90^\circ$. $OP=4$ cm, $PQ=3$ cm and $QR=12$ cm. The perimeter of the pentagon $OPQRS$ is 188 cm.

What is the area, in square centimetres, of the pentagon $OPQRS$?