(define (answer-for-3.1.1)
  '(let ([a 1]) 
     (let ([b 2])
       b)))

(define (answer-for-3.1.2)
  '(let ([a 2])
     (let ([b a])
       b)))

(define (answer-for-3.1.3)
  '(let ([a 2])
     (let* ([b 8] [c b])
       c)))

(define (answer-for-3.1.4)
  '(let ([a (lambda (b) (b b))])
     (a a)))

(define (answer-for-3.1.5)
  '(letrec ([a (lambda (b) (b b))])
     a))

(define (answer-for-3.1.6)
  '(letrec ([a (lambda (b) (a b))])
     (let ([c (lambda (d) 10)]
	   [e (lambda (f) (a f))])
       (e 1))))

(define (answer-for-3.1.7)
  '(letrec ([a (lambda (b) (a b))])
     (letrec ([c (lambda (d) 10)]
	      [e (lambda (f) (c f))])
       (e 1))))

(define (answer-for-3.2.1)
  '(z))

(define (answer-for-3.2.2)
  '(x y z))

(define (answer-for-3.2.3)
  '(z))

(define (answer-for-3.2.4)
  '())

(define (answer-for-3.2.5)
  '(z))

(define (answer-for-3.2.6)
  '(g f y))

(define (answer-for-3.2.7)
  '(g y))

(define (answer-for-3.2.8)
  '(y))

(define (answer-for-3.3.1)
  '(x y))

(define (answer-for-3.3.2)
  '(x y))

(define (answer-for-3.3.3)
  '(y))

(define (answer-for-3.3.4)
  '(z y))

(define (answer-for-3.3.5)
  '(x y))

(define (answer-for-3.3.6)
  '(x g))

(define (answer-for-3.3.7)
  '(f x g))

(define (answer-for-3.3.8)
  '(f x g))

(define-datatype expr expr?
  (number (val number?))
  (id (val symbol?))
  (plus (first expr?)
        (second expr?))
  (let-val (id symbol?)
           (val expr?)
           (body expr?))
  (let-func (id symbol?)
            (func-id symbol?)
            (func-expr expr?)
            (body expr?))
  (app (rator symbol?)
       (rand expr?)))

(define (answer-for-3.4.1)
  (number 1))

(define (answer-for-3.4.2)
  (id 'x))

(define (answer-for-3.4.3)
  (plus (number 1) (number 2)))

(define (answer-for-3.4.5)
  (let-val 'x (number 5) (id 'x)))

(define (answer-for-3.4.6)
  (let-val 'x (let-val 'x (number 2) (id 'x)) (id 'x)))