The mean of the numbers $a, b, 8,5,10$ is $6$ and their variance is $6.8$. If $M$ is the mean deviation of the numbers about the mean, then $25\; M$ is equal to

  • [JEE MAIN 2022]
  • A

    $60$

  • B

    $55$

  • C

    $50$

  • D

    $45$

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  • [JEE MAIN 2023]