def guess_age_group(swimmer_age: int) -> tuple[int, int]:
    """Guess the age group from a swimmer's age.

    Args:
        swimmer_age (int): The swimmer's age.

    Returns:
        tuple[int, int]: The age group in terms of (age_min, age_max).
    """
    if swimmer_age <= 8:
        # Probably 8&U
        return 0, 8
    elif 9 <= swimmer_age <= 10:
        # Probably 9-10
        return 9, 10
    elif 11 <= swimmer_age <= 12:
        # Probably 11-12
        return 11, 12
    elif 13 <= swimmer_age <= 14:
        # Probably 13-14
        return 13, 14
    else:
        # Probably open
        return 0, 109