If the number of ways of selecting 3 numbers out of `1, 2, 3, ……., 2n+1` such that they are in arithmetic progression in 441, then they are in arithemtric progression is 441, then the sum of the divisors of n is equal to

Options

A. 21
B. 22
C. 32
D. None of these

Answer

3

Explanation

`C_(2) +^(n+1)C_(2)=441 rArr (n(n-1))/(2)+((n+1)n)/(2)=441`
`n^(2)=441 rArr n =21`
`"sum of divisors of" 21 = (1+3)(1+7)`
`=4xx8=32`