1 (defun make-sum (a1 a2)
2   (list a1 '+ a2))
3 (defun make-product (m1 m2)
4   (list m1 '* m2))
5 (defun sum? (x)
6   (and (consp x) (eql (cadr x) '+)))
7 (defun addend (x)
8   (car x))
9 (defun augend (s)
10   (caddr s))
11 (defun product? (x)
12   (and (consp x) (eql (cadr x) '*)))
13 (defun multiplier (s)
14   (car s))
15 (defun multiplicand (s)
16   (caddr s))