During a test run, a cable railway car travels the first 400 m of its route in 80 s. It then travels the remaining 1400 m at an average speed of 7.0 m/s.
What is the average speed of the car for the whole route?
6.4 m/s6.4\ \mathrm{m/s}6.4 m/s
7.0 m/s7.0\ \mathrm{m/s}7.0 m/s
9.0 m/s9.0\ \mathrm{m/s}9.0 m/s
6.0 m/s6.0\ \mathrm{m/s}6.0 m/s