Solution:

The sitar can have 18, 19, 20, or 21 strings. Six or seven of these are played strings which run over curved, raised frets, and the remainder are sympathetic strings which run underneath the frets and resonate in sympathy with the played strings.

The “Sangeet Sudarshana” states that the sitar was invented in the 18th century by a fakir named Amir Khusru. This, of course, was a different Amir Khusru from the one who lived in 1300. This latter Amir Khusru was the 15th descendant of Naubat Khan, the son-in-law of Tansen.