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+"""CSC110 Fall 2020 Prep 4: Programming Exercises
+
+Instructions (READ THIS FIRST!)
+===============================
+
+This Python module contains several function headers and descriptions.
+Your task is to complete this module by doing the following for EACH function below:
+
+1. Implement the function so that it does what its description claims.
+
+You do *not* need to add new doctests or preconditions (and in fact
+you should *not* add any preconditions!).
+
+We have marked each place you need to write code with the word "TODO".
+As you complete your work in this file, delete each TODO comment---this is a
+good habit to get into early!
+
+Copyright and Usage Information
+===============================
+
+This file is provided solely for the personal and private use of students
+taking CSC110 at the University of Toronto St. George campus. All forms of
+distribution of this code, whether as given or with any changes, are
+expressly prohibited. For more information on copyright for CSC110 materials,
+please consult our Course Syllabus.
+
+This file is Copyright (c) 2020 David Liu and Mario Badr.
+"""
+from dataclasses import dataclass
+
+
+@dataclass
+class Person:
+    """A person with some basic demographic information.
+    """
+    given_name: str
+    family_name: str
+    age: int
+    address: str
+
+
+def greet_person(person: Person) -> str:
+    """Return a greeting message for the given person.
+
+    The message should have the form 'Hello, <given_name> <family_name>!'
+
+    >>> david = Person('David', 'Liu', 110, '110 St. George Street')
+    >>> greet_person(david)
+    'Hello, David Liu!'
+    """
+    # TODO: complete this function body
+
+
+def older_name(p1: Person, p2: Person) -> str:
+    """Return the first name of the person who is older among p1 and p2.
+
+    If p1 and p2 have the same age, return the name of p1.
+
+    >>> david = Person('David', 'Liu', 110, '110 St. George Street')
+    >>> mario = Person('Mario', 'Badr', 111, '111 St. George Street')
+    >>> older_name(david, mario)
+    'Mario'
+    """
+    # TODO: complete this function body
+
+
+def average_age(people: list[Person]) -> float:
+    """Return the average age of the people in people.
+
+    Preconditions:
+      - people != []
+
+    >>> david = Person('David', 'Liu', 110, '110 St. George Street')
+    >>> mario = Person('Mario', 'Badr', 111, '111 St. George Street')
+    >>> example_people = [david, mario]
+    >>> average_age(example_people)
+    110.5
+    """
+    # TODO: complete this function body
+
+
+@dataclass
+class Group:
+    """A class representing a group of people.
+
+    Its attributes are the group name and a list of the people in the group.
+    """
+    name: str
+    members: list[Person]
+
+
+def member_names(group: Group) -> list[str]:
+    """Return the given names of the members of the given group.
+
+    The names appear in the same order of the members in the group.
+
+    >>> david = Person('David', 'Liu', 110, '110 St. George Street')
+    >>> mario = Person('Mario', 'Badr', 111, '111 St. George Street')
+    >>> cool_profs = Group('Cool Profs', [david, mario])
+    >>> member_names(cool_profs)
+    ['David', 'Mario']
+    """
+    # TODO: complete this function body
+
+
+if __name__ == '__main__':
+    import python_ta.contracts
+    python_ta.contracts.DEBUG_CONTRACTS = False
+    python_ta.contracts.check_all_contracts()
+
+    import doctest
+    doctest.testmod(verbose=True)
+
+    import python_ta
+    python_ta.check_all(config={
+        'extra-imports': ['python_ta.contracts', 'dataclasses'],
+        'max-line-length': 100,
+        'disable': ['R1705']
+    })