The table below shows the number of units produced by five different companies (P, Q, R, S, T) over four consecutive years (2018, 2019, 2020, and 2021). Study the table carefully and answer the questions that follow.
| Company | 2018 | 2019 | 2020 | 2021 |
|---|
| P | 480 | 520 | 600 | 660 |
| Q | 360 | 400 | 450 | 500 |
| R | 540 | 560 | 630 | 690 |
| S | 420 | 480 | 550 | 620 |
| T | 500 | 550 | 580 | 640 |
What is the average number of units produced by Company P, Q, and R in the year 2020?