A, S, M and D are functions of $x$ and $y$, and they are defined as follows:
$A(x, y) = x + y$
$S(x, y) = x - y$
$M(x, y) = xy$
$D(x, y) = \dfrac{x}{y}, \quad y \neq 0$
Let A be the set of 30 students of class XII in a school. Let f : A -> N, N is a set of natural numbers such that function f(x) = Roll Number of student x.
On the basis of the given information, answer the followingIs \( f \) a bijective function?