A student walks 300 m in 60 s, stops for 30 s and then runs 180 m in 30 s.
What is the student's average speed for the whole journey, including the stop?
2.5 m/s2.5\ \mathrm{m/s}2.5 m/s
4.0 m/s4.0\ \mathrm{m/s}4.0 m/s
5.3 m/s5.3\ \mathrm{m/s}5.3 m/s
5.5 m/s5.5\ \mathrm{m/s}5.5 m/s