(define (createRow rows columns)
  (cond
    [(= rows -1) empty]
    [else (cons (list-ref (list-ref a rows) columns)
                (createRow (sub1 rows) columns))]))

(define (loop rows columns)
  (cond
    [(= columns -1) empty]
    [else (cons (reverse (createRow rows columns)) 
                (loop rows (sub1 columns)))]))

(define (transpose mat)
  (cond
    [(empty? mat) empty]
    [else (reverse (loop (- (length mat) 1) (- (length (first mat)) 1)))]))