Answer:
The value is 
Explanation:
From the question we are told that
The emitted frequency increased by 
Let assume that the initial value of the emitted frequency is

Hence new frequency will be 
Generally from Doppler shift equation we have that
![f_1 = [\frac{ v \pm v_o}{v \pm + v_s } ] f](https://tex.z-dn.net/?f=f_1%20%3D%20%20%5B%5Cfrac%7B%20v%20%5Cpm%20v_o%7D%7Bv%20%5Cpm%20%2B%20v_s%20%7D%20%5D%20f)
Here v is the speed of sound with value 
is the velocity of the sound source which is
because it started from rest
is the observer velocity So
Generally given that the observer id moving towards the source, the Doppler frequency becomes
=>
=> 