The frequency of vibration magnetometer of the combination of two bar magnets of magnetic moments $M_1$ and $M_2$ is 6 Hz When like poles are tied and it is 2 Hz when the unlike poles are tied together , then the ratio $M_1 : M_2 $ is :

Question

\[\begin {array} {1 1} (1)\;4:5 & \quad (2)\;5:4 \\ (3)\;1:3 & \quad (4)\;3:1 \end {array}\]