SICP halp for Nubi

Oh wise Lispers and Conjurers of /prog/, I, humble Nubi, seek your enlightenment.  I have started reading SICP, but I'm stuck on an exercise.  I have figured out how to make fast-mult into a logarithmic process, but how do I make it into a tail recursion as well as a logarithmic process?  Here is my code:

; SICP exercise 1-13
; Peasant's algorithm for multiplication
; write a logarithmic iterative process for mult

(define (fast-mult a b)
  (cond ((= b 0) 0)
        ((even? b) (double (fast-mult a (halve b))))
        (else (+ a (fast-mult a (- b 1))))))

(define (double a) (+ a a))
(define (halve a) (/ a 2))

(define (fast-mult2 a b)
  (fast-mult-iter a a b))

(define (fast-mult-iter a n b)
  (cond ((= b 1) n)
        ((and (even? b) (> b 2))
          (fast-mult-iter a (double n) (halve b)))
        (else (fast-mult-iter a (+ a n) (- b 1)))))

(fast-mult 3 2)
(fast-mult2 3 2)
(fast-mult 3 3)
(fast-mult2 3 3)
(fast-mult 3 4)
(fast-mult2 3 4)
(fast-mult 3 5)
(fast-mult2 3 5)
(fast-mult 3 6)
(fast-mult2 3 6)

>>1 Is this a troll? nvm IHBT
>>3
The online version is the 2nd edition, your library's version is probably the 1st edition