3. Explain the algorithm, as well as data structures and language mechanisms used, of the following Scheme code, (define permutations (1ambda (L) return a list of all permutations of list L (let ((insert-all (lambda (e Ls) insert element e into all positions in all lists in Ls (let ((insert-one (lambda (L) insert element e into all positions in list L (letrec (Chelper (lambda (L R) ; insert e in all positions after L in L+R if (nul1? R) (list (append L (list e)) (append (list (append L (list e) R)) (helper (apply append (map insert-one Ls)) (cond ((null? L) 'O) ((null? (cdr L)) (list L)) (else (insert-al1 (car L) (permutations (cdr L))D