Sally is the surveyor in badlands in South Dakota. At point A on south side of the deep canyon, she sights across to the fire tower on north side of canyon at point B. Then she moves the measured 500 feet along south rim of canyon to the point C on the line perpendicular to original sight line AB. Setting up her transit again, she discovers that her line of sight, CB, to tower is 81 degrees. Correct to nearest whole foot, how far is point C from tower?