Answer:
The frequencies are 13.8 Hz, 75 Hz, 12 Hz and 63.8 Hz.
Step-by-step explanation:
Given that,
The frequency in r.p.m




Suppose, we find the frequency in hz.
We know that,
One r.p.m is equal to the one divided by 60 Hz.

We need to calculate the frequency in Hz
Using formula for frequency in Hz
For f₁,



For f₂,



For f₃,



For f₄,



Hence, The frequencies are 13.8 Hz, 75 Hz, 12 Hz and 63.8 Hz.