Calculating the average year of car manufacture by region

There is a class Car containing a license plate number and the year of manufacture of the car. The task is to calculate the average year of manufacture for each region, using the list cars.

class Car:
    def __init__(self, number: str, year: int):
        self.number = number
        self.year = year

cars = [
    Car("a121mm16", 2016),
    Car("c313xx16", 2011),
    Car("b777xx777", 2007),
    Car("a123xx01", 2012),
    Car("c888xx777", 2022),
    Car("b123xx47", 2002),
]

The task involves parsing the car number to obtain the region, grouping cars by region, and calculating the average year of manufacture in each group.