How long after receiving the first p wave from an earthquake centered 4000 km away does a seismic station receive its first S wave from the same earthquake?

The answer is "5 minutes and 35 seconds".

Earthquakes create three kinds of seismic waves which are:P-waves that are primary waves, S-waves that are secondary wavesand surface waves, which land at seismic account stations in a steady progression. Both P and S waves enter the inside of the Earth while surface waves don't. Because of this, P and S waves are known as "body waves"