Physics question from Bmat

idk how to calculate it:))

normal reaction time 0,9s
tired 1,8s
tired + caffeine 1,8 / 3/2 = 1,2s

Between the time he sees the child and the time he reacts by hitting the brakes he will be going at 100m/s. Once he hits the brakes he will be uniformly decelerating until a full stop.

distance between seeing the child and hitting the brakes = distance traveled during the reaction time
d = vt = 100 * 1,2 = 120m

distance between hitting the brakes and a full stop
d = 1/2(u+v)t = 1/2(100+0) * 7 = 350m

total distance = 120+350 = 470 meters
answer C)