Problem: Two identical guitar strings are prepared such that they have the same length (2.56 m) and are under the same amount of tension. The first string is plucked at one location, primarily exciting the 5th harmonic. The other string is plucked in a different location, primarily exciting the 4th harmonic. The resulting sounds give rise to a beat frequency of 315 Hz.

Part A: What is the wave propagation speed on the guitar strings in m/s?

I need help to find the wave propagation speed on the guitar strings.