Exercise 3.3.4:

```;; constant
(define PI 3.142)

;; square : number -> number
(define (square x) (* x x))

;; area-circle : number -> number
(define (area-circle radius)
(* PI (square radius)))

;; circumference-circle : number -> number
(define (circumference-circle radius)
(* 2 PI radius))

;; area-cylinder-side : number number -> number
(define (area-cylinder-side radius length)
(* (circumference-circle radius) length))

;; area-pipe : number number number -> number
;; A pipe has an inside surface and a outside surface
;; and a top and bottom surface.
(define (area-pipe radius length thickness)
(+
(+
(area-cylinder-side radius length)
(area-cylinder-side (+ radius thickness) length))
(*
2
(-
(area-circle (+ radius thickness))
(area-circle radius)))))
```
```;; area-pipe : number number number -> number
;; A pipe has an inside surface and a outside surface
;; and a top and bottom surface.
(define (area-pipe radius length thickness)
(+
(+
(* (* 2 3.142 radius) length)
(* (* 2 3.142 (+ radius thickness) length)))
(*
2
(-
(* 3.142 (* (+ radius thickness) (+ radius thickness)))
(* 3.142 (* radius radius))))))
```