diff --git a/Dockerfile b/Dockerfile
index a370790..e8e21c2 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM haskell:buster
+FROM docker.io/haskell:buster
 
 RUN apt-get update && apt-get install -y haskell-platform
 
diff --git a/code/Angabe5.hs b/code/Angabe5.hs
new file mode 100644
index 0000000..8da21b7
--- /dev/null
+++ b/code/Angabe5.hs
@@ -0,0 +1,183 @@
+module Angabe5 where
+
+{- 1. Vervollstaendigen Sie gemaess Angabentext!
+   2. Vervollständigen Sie auch die vorgegebenen Kommentaranfänge!
+   3. Loeschen Sie keine Deklarationen aus diesem Rahmenprogramm, auch nicht die Modulanweisug!
+   4. Achten Sie darauf, dass `Gruppe' Leserechte fuer Ihre Abgabedatei hat!
+-}
+
+
+type Nat0 = Int
+
+
+-- Die selbstdefinierte Typklasse Menge_von:
+
+class Eq a => Menge_von a where
+   leer          :: [] a
+   vereinige     :: [] a -> [] a -> [] a
+   schneide      :: [] a -> [] a -> [] a
+   ziehe_ab      :: [] a -> [] a -> [] a
+   ist_teilmenge :: [] a -> [] a -> Bool
+   ist_obermenge :: [] a -> [] a -> Bool
+   ist_element   :: a -> [] a -> Bool
+   ist_leer      :: [] a -> Bool
+   sind_gleich   :: [] a -> [] a -> Bool
+   anzahl        :: a -> [] a -> Nat0
+
+   -- Protoimplementierungen
+   leer = []
+   vereinige xs ys     = xs ++ ys
+   ist_teilmenge xs ys = ist_obermenge ys xs
+   ist_obermenge xs ys = ist_teilmenge ys xs
+   ist_element x xs    = anzahl x xs >= 1
+   ist_leer xs         = xs == leer
+   sind_gleich xs ys   = ist_teilmenge xs ys && ist_teilmenge ys xs
+
+
+-- Weitere Typen:
+
+newtype Paar a b = P (a,b) deriving (Eq,Show)
+
+data Zahlraum_0_10 = N | I | II | III | IV | V | VI
+                     | VII | VIII | IX | X | F deriving (Eq,Ord,Show)
+
+newtype Funktion = Fkt { f :: Zahlraum_0_10 -> Zahlraum_0_10 }
+
+data Baum a = Blatt a | Knoten (Baum a) a (Baum a) deriving (Eq,Show)
+
+newtype ElemTyp a = ET a
+
+-- Pseudoheterogene Elementtypen
+data PH_ElemTyp a b c d e = A a | B b | C c | D d | E e deriving (Eq,Show)
+data PH_ElemTyp' q r s    = Q q | R r | S s deriving (Eq,Show)
+
+
+-- Simple helper functions
+roman_to_nat :: Zahlraum_0_10 -> Nat0
+roman_to_nat N = 0
+roman_to_nat I = 1
+roman_to_nat II = 2
+roman_to_nat III = 3
+roman_to_nat IV = 4
+roman_to_nat V = 5
+roman_to_nat VI = 6
+roman_to_nat VII = 7
+roman_to_nat VIII = 8
+roman_to_nat IX = 9
+roman_to_nat X = 10
+roman_to_nat F = -1
+
+nat_to_roman :: Nat0 -> Zahlraum_0_10
+nat_to_roman 0 = N
+nat_to_roman 1 = I
+nat_to_roman 2 = II
+nat_to_roman 3 = III
+nat_to_roman 4 = IV
+nat_to_roman 5 = V
+nat_to_roman 6 = VI
+nat_to_roman 7 = VII
+nat_to_roman 8 = VIII
+nat_to_roman 9 = IX
+nat_to_roman 10 = X
+nat_to_roman n
+   | n > 10 = F
+   | n < 0 = F
+   | otherwise = error "Could not recognize input" -- this should not happen
+
+is_correct_num :: Zahlraum_0_10 -> Bool
+is_correct_num n =
+   case n of
+      F -> False
+      _ -> True
+
+-- Aufgabe A.1
+
+instance Num Zahlraum_0_10 where
+   (+) n n' = add_r n n'
+   (-) n n' = diff_r n n'
+   (*) n n' = mult_r n n'
+   fromInteger n = nat_to_roman (fromInteger n)
+
+add_r :: Zahlraum_0_10 -> Zahlraum_0_10 -> Zahlraum_0_10
+add_r n n'
+   | is_correct_num n == False || is_correct_num n' == False = F
+   | otherwise = nat_to_roman sum_r
+   where
+      a = roman_to_nat n
+      b = roman_to_nat n'
+      sum_r = a + b
+
+diff_r :: Zahlraum_0_10 -> Zahlraum_0_10 -> Zahlraum_0_10
+diff_r n n'
+   | is_correct_num n == False || is_correct_num n' == False = F
+   | otherwise = nat_to_roman dif_r
+   where
+      a = roman_to_nat n
+      b = roman_to_nat n'
+      dif_r = a - b
+
+mult_r :: Zahlraum_0_10 -> Zahlraum_0_10 -> Zahlraum_0_10
+mult_r n n'
+   | is_correct_num n == False || is_correct_num n' == False = F
+   | otherwise = nat_to_roman prod_r
+   where
+      a = roman_to_nat n
+      b = roman_to_nat n'
+      prod_r = a * b
+
+-- Aufgabe A.2
+
+-- instance Eq Funktion where
+--  ...
+
+-- instance Show Funktion where
+--  ...
+
+
+-- Aufgabe A.3
+
+-- instance Menge_von Int where
+--  ...
+
+-- instance Menge_von Zahlraum_0_10 where
+--  ...
+
+-- instance Menge_von Funktion where
+--  ...
+
+
+-- Aufgabe A.4
+
+-- instance (Eq a,Eq b) => Menge_von (Paar a b) where
+--  ...
+
+-- instance Eq a => Menge_von (Baum a) where
+--  ...
+
+
+-- Aufgabe A.5
+
+-- instance Eq a => Eq (ElemTyp a) where
+--  ...
+
+-- instance Show a => Show (ElemTyp a) where
+--  ...
+
+
+-- Aufgabe A.6
+
+-- instance Eq a => Menge_von (ElemTyp a) where
+--  ...
+
+
+
+-- Aufgabe A.7
+
+-- instance (Eq a,Eq b,Eq c,Eq d,Eq e) => Menge_von (PH_ElemTyp a b c d e) where
+--  ...
+
+
+-- Aufgabe A.8
+
+-- instance (Eq p,Eq q,Eq r) => Menge_von (PH_ElemTyp' p q r) where ...
+