Old bachelors look forward to darkness, while Li Nan looks forward to dawn.

Because of the different geographical location, the sunrise time of the eastern coast of China is different from that of the northern border of Northwest China.

What's the difference? Go to the geography teacher to answer this question.

In short, Yue Zitong saw the sunshine when it was just dawn, while Li Nan endured the wind and sand in the darkness before dawn.

The military sent him at a very clever time.

In the early morning, Shulegu County sent him ten kilometers away before the first sandstorm that it experienced every day.

Calculate the time when he...