An earthquake emits both P waves and S waves that travel at different speeds through the Earth. Suppose a P wave travels at 8000 m/s and an S wave at 4000 m/s. If P waves are received at a seismic station 20.0 s before an S wave arrives, how far is the station from the earthquake center?
a. 80 km
c. 240 km
b. 160 km
d. 320 km
B
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A. zero
B. g
C. g/2
D. g/4
E. g/
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