An iron bar having a cross-sectional area of $2 \times 10^{-5} \mathrm{~m}^2$ and magnetising field of $2400 \mathrm{~A} / \mathrm{m}$ produce a magnetic flux $2.4 \pi \times 10^{-5} \mathrm{~Wb}$. What will be the value of permeability $\mu$ and susceptibility $\chi$ of the bar (given, $\mu_0=4 \pi \times 10^{-7}$ )

The magnitude of axial field due to a bar magnet at a distance of 1 m , is found to be $5 \times 10^{-8} \mathrm{~T}$. The magnetic moment of the bar magnet is $\left(\mu_0=4 \pi \times 10^{-7}\right)$

A thin magnetic needle is placed in a magnetic field of 200 G with its axis at $30^{\circ}$ to the direction of the field. Find the magnetic moment of the needle, if it experiences a torque of 0.012 Nm in this field.

Assertion (A) The magnetic field lines are continuous and form closed loops. Reason (R) Magnetic monopole does not exist. The correct option among the following is