For (d) calculate distance travelled by each of the trains and take the difference.
Train A= 0.5bh (for the first 30s) + wb (for the next 66s)
(0.5*30*20) + (66*20)
=1620 m
Train B= 0.5bh ( for the first 90s) + 0.5(h)(a+b) (for the next 6s)
(0.5*90*33.3) + 0.5*6*(33.3+31.08)
=1691.64 m
Seems like Train B is faster hey. So the difference is 71.64 m
ahh seems so much easier now. thankyou so much for your help!