In the given figure, a circle is inscribed in $$\triangle PQR$$, such that it touches the sides PQ, QR and RP at points D, E, F, respectively. If the lengths of the sides $$PQ=15$$ cm, $$QR=11$$ and $$PR=13$$ cm, then find the length of PD.

A

9 cm

B

7.5 cm

C

8 cm

D

8.5 cm