Two bar magnets $\mathrm{A}$ and $\mathrm{B}$ are placed one over the other and are allowed to Vibrate in a vibration magnetometer. They make $20$ oscillations per minute when the similar poles of $\mathrm{A}$ and $\mathrm{B}$ are on the same side, while they make $15$ oscillations per minute when their opposite poles lie on the same side. If ${\mathrm{M}}_{\mathrm{A}}$ and ${\mathrm{M}}_{\mathrm{B}}$ are the magnetic moments of $\mathrm{A}$ and $\mathrm{B}$ and if ${\mathrm{M}}_{\mathrm{A}}>{\mathrm{M}}_{\mathrm{B}}$, the ratio of ${\mathrm{M}}_{\mathrm{A}}$ and ${\mathrm{M}}_{\mathrm{B}}$ is

• A

  $4 : 3$
• Correct answer
  B

  $25 : 7$
• C

  $7 : 5$
• D

  $25 : 16$

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