) Briefly explain what the following function is doing: fun foo 11 12 = foldl (fn (hd, acc) => if (exists 12 hd) then acc else hd ::acc) [] 11 foo: 'a list -> 'a list -> 'a list assuming that function exists is defined as fun exists [] n = false I exists (x:xs) n = if n = x then true else exists xs n For example, what is the result of foo ["a","b", "c"] ["b", "c"]?