## 10. Light Bulbs

In the room, there are two light bulbs. When the switch of the first light bulb is turned on, it lights up after 6 seconds and stays on for 5 seconds, then it turns off for 6 seconds and lights up for 5 seconds again, and this cycle repeats continuously. When the switch of the second light bulb is turned on, it lights up after 4 seconds and stays on for 3 seconds, then it turns off for 4 seconds and lights up for 3 seconds again, and this cycle repeats continuously. Linda turned on both switches at the same time and turned them off after 2021 seconds. How many seconds did both light bulbs light up simultaneously during this time?

Result: 392