I would think that you would have to do 42/2=21Hz, but I'm not sure...
The simple machine that is not correctly matched with its appropriate task is the inclined plane because there is no such big ramp that is as high as 1 storey building, the appropriate task would be Lifting a heavy box and moving it across a room. and for the pulley : <span>Moving a heavy box up to the second floor of a building.</span>
The electric potential energy of the charge is equal to the potential at the location of the charge, V, times the charge, q:

The potential is given by the magnitude of the electric field, E, times the distance, d:

So we have

(1)
However, the electric field is equal to the electrical force F divided by the charge q:

Therefore (1) becomes

And if we use the data of the problem, we can calculate the electrical potential energy of the charge:
The answer should be d because they are constantly rotating