A circle C has center at the origin and radius 9. Another circle K has a diameter with one end at the origin and the other end at the point (0, 10). The circles C and K intersect in two points. Let P be the point of intersection of C and K which lies in the first quadrant. Let (r, 0) be the polar coordinates of P, chosen so that r is positive and 0 ≤ 0 ≤ 2. Find 0​