Two cars leave Denver at the same time and travel in opposite directions. One car travels 10 mi/h faster than the other car. The cars are 660 mi apart in 6 h. How fast is each car traveling?
40 mi/h and 50 mi/h
60 mi/h and 40 mi/h
60 mi/h and 70 mi/h
50 mi/h and 60 mi/h