A childhood game involves tying light gauge polythene papers together and attaching a small mass on one end of the polythene paper string. The mass is swung in a circle using the polythene paper string emitting sound. Suppose a child is rotating a mass at 163 rpm when an observer hears a 0.50 Hz frequency due to the presence of another child rotating a second mass. i) determine two possible rotational frequencies in RPM for the second mass. ii) When the rotational speed of the second mass is decreased, the beat frequency decreases to 0.40 Hz. Which of the values determined in i) is the true rotational frequency of the second mass?