Two bar magnets A,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 A and B are on the same side, While they make 15 oscillations per minute when their opposite poles lie on the same side. If $M_A$ and $M_B$ are the magnetic moments of A and B and if $M_A > M_B$, the ratio of $M_A$ and $M_B$ is :

Question

$$\begin {array} {1 1} (1)\;4:3 & \quad (2)\;25:7  \\ (3)\;7:5 & \quad (4)\;25:16 \end {array}$$