If $x_1, x_2, \ldots, x_n$ are $n$ observations such that $\sum_{i=1}^n x_i^2 = 400$ and $\sum_{i=1}^n x_i = 80$,then the least value of $n$ is

  • A
    $18$
  • B
    $12$
  • C
    $15$
  • D
    $16$

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