The probability that $A$ wakes up before the alarm rings is $0.4$. Then,the mean and variance of the number of times $A$ wakes up before the alarm rings,in the next $7$ days respectively are:

  • A
    $0.4, 0.6$
  • B
    $2.8, 0.6$
  • C
    $2.8, 1.68$
  • D
    $7, 0.6$

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