Without more details, I just have to assume that the 406 km is the displacement ... that is, the straight-line distance between the start point and the end point. If there were any turns, loops, or backtracks during the trip, then this question couldn't be answered, because we don't know the displacement.
a). Average velocity = (406 km) / (7.0 hours) = 58 km/hr West.
According to the requirements stated in the question, I still have to convert this answer to a different unit in order to rightfully claim the full 5-points bounty.
b). (58 km/hour) x (1,000 m/km) x (1 hour / 3600 sec) = 16-1/9 m/sec .
