For the set N of natural numbers and a binary operation f : N x N → N, an…

For the set N of natural numbers and a binary operation f : N x N → N, an element z ∊ N is called an identity for f, if f (a, z) = a = f(z, a), for all a ∊ N. Which of the following binary operations have an identity?

1. f (x, y) = x + y - 3

2. f (x, y) = max(x, y)

3. f (x, y) = xy