The drawing shows an arrangement in which a block (mass = 21.6 kg) is held in position on a frictionless incline by a cord (length = 0.700 m). The mass per unit length of the cord is 0.960 x 10-2 kg/m so the mass of the cord is negligible compared to the mass of the block. The cord is being vibrated at a frequency of 142 Hz (vibration source not shown in the drawing). What is the maximum value of the angle ?in degrees at which a standing wave pattern exists on the cord?