#| BEGIN (Write your solution here) |#
; Code from the book
(define (=number? exp num) (and (number? exp) (= exp num)))
(define (make-sum a1 a2) (cond ((=number? a1 0) a2) ((=number? a2 0) a1) ((and (number? a1) (number? a2)) (+ a1 a2)) (else (list '+ a1 a2))))
(define (make-product m1 m2) (cond ((or (=number? m1 0) (=number? m2 0)) 0) ((=number? m1 1) m2) ((=number? m2 1) m1) ((and (number? m1) (number? m2)) (* m1 m2)) (else (list '* m1 m2))))

; My code
(define (install-sum-package)
    (define (addend exp) (car exp))
    (define (augend exp) (cadr exp))
    (define (inner-deriv exp var) (make-sum (deriv (addend exp) var) (deriv (augend exp) var)))
    (put 'deriv '+ inner-deriv)
    'done
)
(define (install-product-package)
    (define (multiplier exp) (car exp))
    (define (multiplicand exp) (cadr exp))
    (define (inner-deriv exp var) (make-sum (make-product (multiplier exp) (deriv (multiplicand exp) var)) (make-product (deriv (multiplier exp) var) (multiplicand exp))))
    (put 'deriv '* inner-deriv)
    'done
)
#| END |#