In △PQR\triangle PQR△PQR, if p=11p=11p=11, q=13q=13q=13, and ∠R=60∘\angle R = 60^\circ∠R=60∘, find the length of side rrr.
2312\sqrt{31}231
737\sqrt{3}73
121212
147\sqrt{147}147