Determine the horizontal distance between two points A and B whose elevations above datum are hA = 1560 ft. and hB = 1425 ft. and whose images a and b on a vertical photograph have photo coordinates xa = 2.95 in., ya = 2.32 in., xb = -1.64 in., and yb = -2.66 in. The camera focal length was 152.4 mm and the flying height above datum 7500 ft.