**Exercise 2.5:** Show that we can represent pairs of nonnegative integers using only numbers and
arithmetic operations if we represent the pair `a`

and `b`

as the integer that is the product
2a 3b. Give the corresponding definitions of the procedures `cons`

,
`car`

, and `cdr`

.

The discrete log procedure is a cousin of `discrete-log`

from 1.45.

```
(define (cons a b)
(* (expt 2 a) (expt 3 b)))
(define (car x)
(discrete-log x 2))
(define (cdr x)
(discrete-log x 3))
(define (discrete-log n base)
(if (not
(= 0 (remainder n base)))
0
(+ 1 (discrete-log (/ n base) base))))
```