There's no information to describe the DIRECTION of the motion
at any time, so I'll have to work with speed instead of velocity.
__________________________
Average speed = (total distance covered) / (time to cover the distance)
Distance covered in the first 8 seconds = 60 meters)
Distance covered in the middle 16 seconds = 240 meters
Distance covered in the last 21 seconds = 157.5 meters
Total distance covered = 457.5 meters
Time to cover the distance = 45 seconds
Average speed = (457.5 meters) / (45 seconds) = 10.17 m/s .
____________________________________
Average acceleration = (change in speed) / (time for the change)
Speed at the beginning = 0
Speed at the end = 0
Change in speed = 0
Time for the change = 45 seconds
Average acceleration = 0/45 = 0 .