1 and b are affected by typhoon. Make a vertical line from B, and BD is perpendicular to AC. As long as BD is smaller than the typhoon radius, it will be affected by the typhoon.

BD = ab×sin(π/6)= 20× 16×sin(π/6)= 160 mile & lt； 200 miles

2. Assuming that the distance between points E and F on AC and point B is 200mile, the time for typhoon to walk on EF section is the time for point B to be affected by typhoon.

Because be = BF = 200, BD = 160, BD is perpendicular to AC, so it can be obtained according to Pythagorean theorem.

ef=2de=2df=2×√(200^2- 160^2)=2× 120=240mile

240/40 = 6 hours

The impact time is 6 hours.

3. In order to avoid being affected by the typhoon, that is, unloading is completed before the typhoon reaches point E, so the unloading time should be shorter than the travel time of the typhoon on the AC section.

Because BD is perpendicular to AC,

So ad = ab× cos (π/6) = 20×16× √ 3/2 =160 √ 3 miles.

AE=AD-DE= 160√3

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120

t=AE/v=( 160√3

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120)/40

≈3.93 hours