#| BEGIN (Write your solution here) |#
(define (halve x) (/ x 2))
(define (double x) (+ x x))

(define (mul-iter a b)
  (define (iter a b re)
    (cond ((= b 0) re)
          ((even? b) (iter (double a) (/ b 2) re))
          (else (iter a (- b 1) (+ re a)))))
  (iter a b 0))
#| END |#