A rock climbing enthusiast is creating a climbing route rated as 5.8 level (i.e., medium difficulty) on the wall at the local rock gym. Given the difficulty of the route, he wants to avoid placing any two holds on the same vertical or horizontal line on the wall. If he places holds at P, Q, and R such that ?QPR = 40°, QR = 6 feet, and QP = 4.5 feet, how far is the hold at P from the hold at R?