A square frame of wire `abcd` of side `1 m` has a total resistance of `4 Omega`.It is pulled out of a magnetic field `B=1 T` by applying a force of `1 N` (figure).It is found that the frame moves with constant speed.Find (a)this constant speed. (b)the `emf` induced in the loop, (c) the potential difference between the points `a` and `b` and (d)the potential difference between the points `c` and `d`.