A large tent is being set up for a fair. Two poles, QU and RT, are placed perpendicular to the ground and 12m apart. Pole QU is 4m in length and pole RT is 7.5m in length. A tarp is placed over the poles and secured to the ground at P, 3m from the base of pole QU, and S, 4m from the base of pole RT. Determine PQ+QR+RS; the length of the tarp.