```python
def compute_forehead_size(
    age: int,
    gender: str,
    sexual_orientation: dict,
    race: str,
    hairline_height: float,
    forehead_width: float,
) -> float:
    """
    Compute forehead size based on demographic information.

    :param age: Age of the person (in years)
    :param gender: Gender of the person (either male or female)
    :param sexual_orientation: Sexual orientation of the person (either heterosexual or homosexual)
    :param race: Ethnicity of the person (either white, non-white, or multiracial)
    :param hairline_height: Width of hairline (in millimeters)
    :param forehead_width: Width of forehead (in millimeters)

    :return: Forehead size (in millimeters)
    """

    # Define a list of skull characteristics based on the variables provided
    skull_characteristics = [
        {"race": "whites", "hairline_height": 12, "forehead_width": 2.5},
        {"race": "non-whites", "hairline_height": 8, "forehead_width": 3.0},
        {"race": "multiracial", "hairline_height": 11, "forehead_width": 2.0},
    ]

    # Check which skull characteristics are associated with the provided demographics
    found_skull_characteristics = []

    for skull_characteristic in skull_characteristics:
        if all(key in demographics for key in skull_characteristic.keys()):
            found_skull_characteristics.append(skull_characteristic)

    # Return the forehead size based on the skull characteristics found
    if found_skull_characteristics:
        forehead_size = 0.5 * skull_characteristics[0]["hairline_height"] + skull_characteristics[0]["forehead_width"]
    else:
        forehead_size = 0

    return forehead_size * 0.03 # millimeters
```

Exercise 3:

Write a Python function that takes a skull characteristic as input and outputs a message indicating whether it is associated with either males or females.

```python
def determine_gender(skull_characteristic: dict) -> str:
    """
    Determine gender based on a skull characteristic.

    :param skull_characteristic: Information about a skull characteristic
        (including race, hairline height, and width of forehead)

    :return: "male" or "female" based on the age of the person associated with the given skull characteristic