[plt-scheme] HTDP Exercise 12.4.2 ... Help!

> (define (insert-everywhere/in-all-words s a-low)
>  (cond
>    ((empty? a-low) ... s ...)
>    (else ... s ... (first a-low) ...
>            ... (insert-everywhere/in-all-words s (rest a-
> low)) ... )))
>

Assume a-low is not empty.

(insert-everywhere/in-all-words s (rest a-low))

What does the above represent? Obviously, it is part of the answer but
not the whole answer. Why? What's missing?

What do you need to do to compute what is missing using s and (first
a-low)? Is what is missing of arbitrary size? If so, design and create
an auxilary function to compute it.

Finally, how to you put together the result you want from the results
you get from the two steps above?

-- 

Cheers,

Marco