3.) Write a Scheme function flat-min-string that takes a flat, non-empty list of strings and returns the lexicographically least string in the list. Your implementation must use Scheme foldl. You'll need to put

 (require (lib "list.ss"))}

in your code to use foldl. Examples:

 (flat-min-string '("millipede" "centipede" "spider")) =>
     "centipede"
 (flat-min-string '("a" "aa" "aaa")) => "a"

4.) Use a named let instead of foldl to implement flat-min-string.