[racket] Cube two numbers

Slight tangent:

Can you please point out which curriculum you are using to learn from,
as it seems weird.  It's almost as if you're making things hard for
yourself.  Could it be that the curriculum's to blame?  I've never
seen an intro programming class start off with using lambda when one
hasn't yet seen functions with multiple arguments.  I guess there's a
first time for anything... :(

If it's your professor's own homebrewed thing, please point your
professor to something like How to Design Programs
http://www.ccs.neu.edu/home/matthias/HtDP2e/