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If the number of ways in which 7 letters...

If the number of ways in which 7 letters can be put in 7 envelopes such that exactly four letters are in wrong envelopes is N, then

A

Number of divisors of N is 12

B

Sum of proper divisors of N is 624

C

Number of divisors of N which are divisible by 3 but not by 9 is 4

D

Sum of proper divisors of N is 309

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A
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