;;; Trees
(define (burned-tree? tr1 tr2)
  (and (= (datum tr1) (datum tr2))
       (burned-forest? (children tr1) (children tr2))))

(define (burned-forest? fr1 fr2)
  (cond ((null? fr1) #t)
        ((null? fr2) #f)
        (else (or (and (burned-tree? (car fr1) (car fr2))
                       (burned-forest? (cdr fr1) (cdr fr2)))
                  (burned-forest? fr1 (cdr fr2))))))

;;; Recursion and Higher-Order Functions
(define (product-list ls)
  (if (null? ls)
      '()
      (cons (car ls)
            (map (lambda (num) (* num (car ls)))
                 (product-list (cdr ls))))))

;;; Orders of Growth
O(n^4) in both cases (the constant factor of 4/3 pi in the second subpart will be ignored).