Two wires with current 3A and 1.5A are enclosed in a circular loop P. Third parallel wire with current 1A is situated outside the loop as shown. All the wires are perpendicular to the plane of the circular loop. The value of $\oint \vec{B} \cdot \vec{dl}$ around the loop is ($\mu_0 = $ permeability of free space)

Two coils A and B have 180 and 360 turns respectively. The current of 1A flows through both the coils. Due to current of 1A in coil A, flux per turn of $0.8 \times 10^{-3}$ Wb is linked with coil A. Due to current of 1A in coil B, flux per turn of $1 \times 10^{-3}$ Wb is linked with coil B. The self inductance of coil A is $L_A$ and the self inductance of coil B is $L_B$. The ratio $L_A$ to $L_B$ is

If current of 4 A produces magnetic flux of $3 \times 10^{-3}$ Wb through a coil of 400 turns, the energy stored in the coil will be

The equivalent inductance between A and B is equal to