The painting is not good, but it can be seen clearly;

The shortest distance of AC is the distance when AC⊥BC, that is, = AB× SIN ∠ B = 300× SIN 30 = 150.

Location A starts at the typhoon center M and ends at N. ..

Influence distance mn? =? mc？ +? North Carolina (USA)

Pythagorean theorem: mc? =? nc？ =? 80

So mn? =? 160

So the time is 160? /? 20? =? 8? Hours,