(define (accumulate op initial sequence)
  (if (null? sequence)
      initial
      (op (car sequence)
          (accumulate op initial (cdr sequence)))))

(define (accumulate-n op init seqs)
  (if (null? (car seqs))
    '()
     (cons (accumulate op init (map car seqs))
           (accumulate-n op init (map cdr seqs)))))

; 1 ]=> (accumulate-n + 0 '((1 2 3) (4 5 6) (7 8 9) (10 11 12)))
; 
; ;Value: (22 26 30)