Ok,
Let's check to see if he catches it before he reaches 8 m/s.
Velocity = acceleration * time, V = at,
so 8 m/s = 3.4 m/s * t, so t = 2.35 sec
in that time he moved
Distance = Initial Velocity * time + 1/2 acceleration * time * time
S = 0*2.35 + 1/2*3.4*2.35*2.35 = 9.4 meters
in 2.35 seconds, the boxcar moved
S = V*t = 4.5 * 2.35 = 10.59 meters, so he still needs to catch up
10.59 m - 9.4 m = 1.19 meters. Since he is now moving at 8 m/s and the train is moving at 4.5 m/s, his closing speed is (8 - 4.5) = 3.5 m/s
It will take him 1.19m/3.5m/s = .34 seconds more to catch up.
So answer A is 2.35 sec + .34 sec = 2.69 seconds.
For answer B we use the speed of the train since it was constant,
Distance = Velocity * time = 4.5 m/s * 2.69 s = 12.1 meters.
I hope my answer has come to your help. Thank you for posting your question here in Brainly.