In quadrilateral PQRS, P = (0, 0), Q = (a + c, 0), R = (2a + c, b), and S = (a, b). How can you use coordinate geometry to show that the diagonals are perpendicular? OA Find the slopes of PQ and RS, and show that their product is -1. OB Apply the Distance Formula to show that opposite sides PQ and RS are congruent. Oc C Apply the Distance Formula to show that opposite sides PS and QR are congruent. D Find the slopes of PR and QS, and show that their product is -1.