[填空题]
A tight guitar string has a frequency of 540 Hz as i :c-o ,dz l7 /v.wexvhv9g3i fso/lxj;oho;0its third harmonik)gq l z*rbjq+jgbd : g*oh*04c. What will be its fundamental frequency if it is fingered at a length of only 60% of its original length?z*qjgqdjg4l 0b+ k:hr)ogb** Hz