Answer:
![f' = 410 Hz](https://img.qammunity.org/2020/formulas/physics/high-school/zrhxd895ctfgxxf0ew8pwg0nr5lvruz0vx.png)
Step-by-step explanation:
Initially when fundamental frequency of the string is
f = 328 Hz
let the length of the string is Lo at this time
so we will have
![f = (2v)/(L_o)](https://img.qammunity.org/2020/formulas/physics/high-school/bxcrox8bvodw5xwy7ohyluni1bl6hhuq3x.png)
now the length is shorten so that the frequency will change
final length is four fifth of the original length
so here we have
![L = (4L_o)/(5)](https://img.qammunity.org/2020/formulas/physics/high-school/h8lk9472n6cxny3ioevd693yphpxksi20i.png)
now we have
![f' = (2v)/(4L_o/5)](https://img.qammunity.org/2020/formulas/physics/high-school/gr675wkzdpt83rx9f0crsdiff30jvnj8zc.png)
![f' = (5v)/(2L_o)](https://img.qammunity.org/2020/formulas/physics/high-school/rwifqs505uu7ymsj0x6saq8ypcsfhi15x3.png)
now we have
![(f')/(f) = (5v/2L_o)/(2v/L_o)](https://img.qammunity.org/2020/formulas/physics/high-school/zjk464ywktubo03w406001agc0l0oumtav.png)
so we have
![(f')/(f) = (5)/(4)](https://img.qammunity.org/2020/formulas/physics/high-school/cmv87dsz1r3h2bim12jaxz6eny9evoyx67.png)
so the new fundamental frequency will be
![f' = (5)/(4)(328)](https://img.qammunity.org/2020/formulas/physics/high-school/93b2l97z3ci79en7mb9180vo7msmluwr3s.png)
![f' = 410 Hz](https://img.qammunity.org/2020/formulas/physics/high-school/zrhxd895ctfgxxf0ew8pwg0nr5lvruz0vx.png)