What is the magnetic susceptibility of a superconductor?

Curie's law can be written as

Fill in the blank :
$(i)$ The domain size is ...... .
$(ii)$ The domain contains about ...... atoms.

$A$ ferromagnetic material is heated above its $Curie$ temperature. Which one is a correct statement?

$A$ susceptibility of a certain magnetic material is $ 400 $. What is the class of the magnetic material $ ? $

Explain quantitatively the order of magnitude difference between the diamagnetic susceptibility of ${N_2} \left( { \sim 5 \times {{10}^{ - 9}}} \right)$ (at $STP$) and ${Cu} \left( { \sim {{10}^{ - 5}}} \right)$.