A sample of paramagnetic salt contains $2 \times 10^{24}$ atomic dipoles each of dipole moment $1.5 \times 10^{-23} \mathrm{JT}^{-1}$. The sample is placed under homogeneous magnetic field of 0.6 T and cooled to a temperature 4.2 K. The degree of magnetic saturation achived is $20 \%$. Then total dipole moment of the sample for a magnetic field of 0.9 T and a temperature of 2.8 K is

• A

  $4.5 \mathrm{~J} \mathrm{~T}^{-1}$
• Correct answer
  B

  $13.5 \mathrm{~J} \mathrm{~T}^{-1}$
• C

  $0.64 \mathrm{~J} \mathrm{~T}^{-1}$
• D

  $7 \mathrm{~J} \mathrm{~T}^{-1}$

Hence, the correct answer is option: 'B'.