Give the answer .

The method is clear enough . 

But put clearly the value of dx/dt  . Can't read properly .

I have taken that to be a/sqrt(x ) . In that case , the answer is pretty correct !!

The answer ( more precisely the value of c) would be different (  a factor of 4pi epsilon naught would be present ) if the calculation is done in SI method .But in that case also q must be proportioal to time .

Also the qn is incomplete !! It has not mentioned what initial charge was present in the balls . I have taken that to be zero .

Are u having problem with the value of c ? Let me know !