Answer:
Average speed = 25m/s
Acceleration = 12.5m/s^2
Explanation
Let the distance covered by Riley be 50m
Average speed = Distance/Time
Average speed = 50/2
Average speed = 25m/s
Acceleration = Speed/time
Acceleration = 25/2
Acceleration = 12.5m/s^2
Note that the value of the distance was assumed