A2)a)

mapList :: (Int -> Int) -> List -> List
mapList _ [] = []
mapList f (x:xs) = f x : maplist f xs

b)
negateList :: List -> List
neagteList xs = mapList (\x -> -x) x:xs

c)
foldList :: (Int -> a -> a) -> a -> List -> a
foldList f c Nil = c
foldList f c Cons( a n) = f a (foldList f c n)