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Geologists use explosives to map subterranean. The time for the reflected waves to arrive at a monitoring station can tell a great deal about the composition of the rock structures. suppose the time it takes for a wave that is reflected from the interface of 1 and 2 is 2s, and the time for another wave that is reflected between 2 and 3 is 2.5s, and the speed of the wave in layer 1 is 6 km//s and in layer 2 is 4 km/s, then how thick is layer 2?
a.)1 km
b.)8 km
c.)3 km
d.)2 km
e.)6 km