[plt-scheme] HTDP Exercise 17.1.2

I am trying to solve this particular exercise from htdp(17.1.2) .I have two
questions here :-

1) In the data definition of los and lon do I have to consider the empty
list scenario?
2) The design recipe before the example explains that one list can be
considered atomic but in this case requires to extract each element from the
two lists make a list of that and then make a list of all the lists.So how
do I go about the recursion?


Please point me in the right direction.


Aditya
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