A string on an instrument (0.9 m long) carries travelling waves at 180 m/s. What are the 3 lowest notes?

Lucious C asked: A string on a musical instrument (0.9 m long) carries travelling waves at 180 m/s.
a.) What are the three lowest notes that this string can play (keeping the string at its full length)?
lowest:__Hz
second to lowest:__Hz
third to lowest:__Hz
b.) If a note was “fretted”, by reducing the length of the string to 0.225 [...]