19. l\" A 500 kg piano is being lowered into position by a crane while two people steady it with ropes pulling to the sides. Bob's rope pulls to the left, 15 below horizontal, with 500 N of ten sion. Ellen's rope pulls toward the right, 25 below horizontal. a. What tension must Ellen maintain in her rope to keep the piano descending vertically at constant speed? b. What is the tension in the vertical main cable supporting the piano