Answer:
It needs to be 78 mi/h, equivalent to 34.9 m/s.
Step-by-step explanation:
From its definition, the average speed is calculated dividing the total distance traveled by the interval of time that lasts the travel. It means that we can calculate your needed average speed using the equation:

Where
is your average speed,
is the distance between you and the city, and
is the interval of time of the journey. Then, substituting the known values, we get:

It means that your average speed needs to be 78 miles per hour, around 34.9 meters per second.