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Let N be the set of natural numbers and two functions f and g be defined as f, g : N N → such that f(n) = ⎪ ⎩ ⎪ ⎨ ⎧ + even is n if ; 2 n odd is n if ; 2 1 n ; and g(n) = n – (–1) n . Then fog is

1. neither one-one nor onto
2. onto but not one-one
3. both one-one and onto
4. one-one but not onto

Correct answer: onto but not one-one

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