The arithmetic mean and standard deviation of a data set of nine numbers are $13$ and $5$ respectively. If $3$ is included as the $10^{th}$ item of the data,then the variance of the data set of ten numbers is:

  • A
    $23.5$
  • B
    $21.5$
  • C
    $31.5$
  • D
    $27$

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