A radio-active material is reduced to $1 / 8$ of its original amount in $3$ days. If $8 \times 10^{-3}\,kg$ of the material is left after $5$ days. The initial amount of the material is $.......\,g$

  • [JEE MAIN 2023]
  • A

    $64$

  • B

    $40$

  • C

    $32$

  • D

    $256$

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