diagram

((a -> b) -> c) -> (d -> (e -> f))

         ->
       /    \
     ->      ->
    /  \    /  \
  ->    c  d    ->
 /  \          /  \
a    b        e    f

Exercise.hs

import Data.Functor.Contravariant

data Foo a = Foo (a -> Integer)

data Bar a = Bar ((a -> Integer) -> Integer)

data Baz a = Baz (((a -> Integer) -> Integer) -> Integer)

foo :: (b -> a) -> (a -> Integer) -> (b -> Integer)
foo f g = _

bar :: (a -> b) -> ((a -> Integer) -> Integer) -> ((b -> Integer) -> Integer)
bar f g = _

baz :: (b -> a) -> (((a -> Integer) -> Integer) -> Integer) -> (((b -> Integer) -> Integer) -> Integer)
baz f g = _

instance Contravariant Foo where
  contramap f (Foo g) = Foo (foo f g)

instance Functor Bar where
  fmap f (Bar g) = Bar (bar f g)

instance Contravariant Baz where
  contramap f (Baz g) = Baz (baz f g)