Exercise 4.2.1:

1. the interval (3,7]:

```;; is-between-3-excl-7-incl? : number -> number
;; to determine whether n is between 3 (exclusive)
;; and 7 (inclusive)
(define (is-between-3-excl-7-incl? n)
(and (< 3 n) (<= n 7)))
```

2. the interval [3,7]:

```;; is-between-3-incl-7-incl? : number -> number
;; to determine whether n is between 3 (inclusive)
;; and 7 (inclusive)
(define (is-between-3-incl-7-incl? n)
(and (>= n 3) (<= n 7)))
```

3. the interval [3,7):

```;; is-between-3-incl-9-excl? : number -> number
;; to determine whether n is between 3 (inclusive)
;; and 9 (exclusive)
(define (is-between-3-incl-9-excl? n)
(and (>= n 3) (< n 9)))
```

4. the union of (1,3) and (9,11):

```;; is-between-1-3-or-9-11? : number -> number
;; to determine whether n is between 1 and 3 (exclusive)
;; or 9 and 11 (exclusive)
(define (is-between-1-3-or-9-11? n)
(or
(and (< 0 n) (< n 4))
(and (< 8 n) (< n 12))
))
```

5. and the range of numbers outside of [1,3]:

```;; is-under-1-or-over-3? : number -> number
;; to determine whether n less than 1 (inclusive)
;; and greater than 3 (inclusive)
(define (is-under-1-or-over-3? n)
(or (<= n 1) (>= n 3)))
```