Two infinitely long parallel conducting wires $A$ and $B$ carry currents $I$ and $2I$, respectively, in the same direction. The wire $A$ has uniform mass per unit length $\lambda$ and lies on an insulated floor. The wire $B$ is kept fixed at a height $h$ above the floor. The minimum magnitude of $h$ so that the 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]

• A
  $\frac{\mu_0 I^2}{2\pi \lambda g}$
• B
  $\frac{\mu_0 I^2}{\pi \lambda g}$
• C
  $\frac{2\mu_0 I^2}{\pi \lambda g}$
• D
  $\frac{4\mu_0 I^2}{\pi \lambda g}$