60 north to west ∠ ABC = 30 AB = 300

AC= 150 will be affected by typhoon.

(2) At the beginning of the impact, the typhoon center O 1 is 200 away from A city, that is, O 1A=200.

AC= 150, so O 1E=50√7.

When the typhoon left, the typhoon center O2 was 200 away from A city.

O2A=200 so O2E=50√7.

So from O 1 to O2, the typhoon center went to 100√7.

The time affected by typhoon is100 √ 7/10 √ 7 =10 hour.