A magnet freely suspended in a vibration magnetometer makes 10 oscillations per minute at a place A and 20 oscillations per minute at a place B. If the horizontal component of earth?s magnetic field at A is \[36\times {{10}^{-6}}T,\] then its value at B is [EAMCET (Med.) 2001]

• A.            36 ´ 10?6 T                             
• B.            72 ´ 10?6 T
• C.            144 ´ 10?6 T                           
• D.            288 ´ 10?6 T