Study the following table showing annual production (in '000 units) of three factories P, Q, R over five years: Year | P | Q | R 2019 | 100 | 150 | 200 2020 | 120 | 180 | 180 2021 | 150 | 160 | 220 2022 | 200 | 200 | 240 2023 | 250 | 220 | 260 In which year was the combined production of all three factories the highest?