A thin 2 m long string with mass 3 g is stretched with a tension 90 N between two ends.

A thin 2 m long string with mass 3 g is stretched with a tension 90 N between two ends. When it vibrates with the third harmonic the amplitude of the string at an antinode A of the standing wave on the string has an amplitude of 5 cm. a) What is the speed of propagation of waves in the string? b) What is the maximum transverse speed of this point A on a string? c) What is the total power of the string vibrations?