A radioactive material decays by simultaneous emission of two particles with respective half lives $1620$ and $810$ years. The time (in years) after which one- fourth of the material remains is

  • [IIT 1995]
  • [AIIMS 2008]
  • A

    $1080$

  • B

    $2430$

  • C

    $3240$

  • D

    $4860$

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