In an experiment on standing waves, a mechanical vibrator drives a string. Both ends of the string are fixed. The distance between the fixed ends is 80.0 cm. Tension in the string is produced by hanging a mass over a pulley. At 60.0 Hz, 5 antinodes are observed on the string. If the mass per unit length of the string is 0.049 kg/m, how much mass is hanging over the pulley.