Let $A = \hat{i} + 2 \hat{j}$. If $B$ is a vector in the $XY$ plane such that $(A + B) \cdot B = 15$ and $A \cdot B = 6$,then $|B|$ is

  • A
    $6$
  • B
    $9$
  • C
    $15$
  • D
    $3$

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