Starting with a sample of pure ${}^{66}Cu,\frac{7}{8}$ of it decays into $Zn$ in $15\, minutes$. The corresponding half life is..........$minutes$

  • [AIIMS 2008]
  • A

    $15$ 

  • B

    $10$ 

  • C

    $7\frac{1}{2}$

  • D

    $5$

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