The net energy of 1 ton of coal is 2.8 x 10^6 BTU. The cost of extracting the coal, transporting it, and burning it is 4.2 x 10^6 BTU. What was the gross energy of the coal?

Many archeologists and anthropologists disagree with dr. thorne's view.  thorne strongly believes that what many calls "homo erectus"  was in fact  homo sapiens,  and that they migrated out of africa almost 2 million years ago and dispersed throughout europe and asia. that's way different  from what scientists have always believed about the evolution of the species.

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