In a school, the average age of students is $6 \,years$ , and the average age of $12$ teachers is $40\, years.$ If the average age of the combined group of all the teachers and students is $7 \,years$ , then the number of students is?

  • A

    $396$

  • B

    $400$

  • C

    $408$

  • D

    $416$

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