The 14 hour limit can be extended by `_________`.

A Spending 8 consecutive hours in a sleeper berth

explanation

You may also use the sleeper berth to extend the 14 hour limit. Any period in the sleeper berth of at least 8 consecutive hours will not count as part of the 14 hours, and therefore, would allow you to extend the time during which you could use your maximum 11 hours of driving.