Radon (Ra) decays into Polonium (\[{{P}_{0}}\]) by emitting an \[\alpha -\]particle with half-life of 4 days. A sample contains \[6.4\times {{10}^{10}}\]atoms of\[Rn\]. After 12 days, the number of atoms of \[{{R}_{n}}\]left in the sample will be [MP PET 1999, Pb. PMT 2004]

• A.            \[3.2\times {{10}^{10}}\]
• B.            \[0.53\times {{10}^{10}}\]
• C.            \[2.1\times {{10}^{10}}\]
• D.            \[0.8\times {{10}^{10}}\]