KöMaL 2018 K601

The sides of a square $PQRS$ inscribed in an acute-angled triangle $ABC$ are 4 cm long, vertices $P$ and $Q$ lie on side $AB$, vertex $R$ lies on side $BC$, and vertex $S$ lies on side $AC$. Given that the length of side $AB$ is 8 cm, what is the area of the triangle?