Average velocity = (displacement) / (travel time)
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 .
