2. Solution. A one-way trip takes 2 hours and 40 minutes, so a round trip takes 5 hours and 20 minutes. Therefore, after a round trip, the driver must rest for at least one hour.

Let's call the drivers of the first, second, and third trips A, B, and C, respectively. Driver A returns to the station at 12:40. At this time, drivers B and C are still on the road. Driver A cannot start his next trip earlier than 13:40, so there must be a fourth driver D, who departs from the station at 13:05.

Four drivers are sufficient. Driver A departs on the fifth trip at 16:10, and driver B, who returns to the station at 16:00, has enough time to rest and departs on the sixth trip at 17:30.

If driver A departs on a trip at 17:30, the trip at 16:10 will be left without a driver: at this time, driver B has not yet rested, and drivers C and D are still on the road. Therefore, driver A performs the trip from 16:10 to 21:30, which brings Alexei Ivanovich back to the station.
Answer: 4 drivers; at $21:30$.

## Grading Criteria

| Full Solution | 2 points |
| :--- | :--- |
| It is shown that there should be four drivers, but there is no explanation that the driver of the first trip was on duty at 16:10 | 1 point |
| No solution, or incorrect (even if the correct answer is given) | 0 points |