$20.$ Two parallel wires, $4$ cm apart, carry currents of $2$ A and $4$ A respectively, in the same direction.

The force per unit length of one wire on the other is:

A$)1103$ N$/$m$,$ repulsive

B$)1103$ N$/$m$,$ attractive

C$)4105$ N$/$m$,$ repulsive

D$)4105$ N$/$m$,$ attractive

E$)$ none of these