Moving Charges and Magnetism (Force Between Wires)

Two infinitely long parallel conducting wires A and B carry currents I and 2I respectively in the same direction. Wire A has uniform mass per unit length lambda and lies on an insulated floor. Wire B is kept fixed at a height h above the floor. The minimum magnitude of h so that wire A does not rise from the floor is: [g is the acceleration due to gravity and mu_0 is the permeability of free space.]