If `N` denotes the set of all positive integers and if `f : N -> N` is defined by `f(n)=` the sum of positive divisors of `n` then `f(2^k*3)`, where k is a positive integer is

Options

A. `2^(k+1) -1`
B. `2(2^(k+1)-1)`
C. `3(2^(k+1)-1)`
D. `4(2^(k+1)-1)`

Answer

C