A, S, M and Dare functions of x and y, and they are defined as follows:
$A(x, y) + x + y$
$S(x, y) = x - y$
$M(x, y) = xy$
$D(x, y) = x/y$,
where $y \neq 0$.
What is the value of S(M(D(A(a, b), 2), D(A(a, b),2)), M(D(S(a, b), 2), D(S(a, b),2)))
- $a^{2} b^{2}$
- $ab$
- $a^{2} –b^{2}$
- $a/b$