Let's start with distance covered by the train from Stanton to Dunhill. It covered 3/4th of the total distance from Stanton (i.e. 1/4th from Dunhill) by 11:55 AM, and reached Dunhill by 12:20 PM, i.e. in
25 minutes.
Since the train from Stanton took 25 minutes to cover 1/4th of the distance, at constant speed, it must've taken 25 x 3 = 75 minutes to cover 3/4th of the distance from the starting point in Stanton, i.e the train had begun it's journey by
10:40 AM.
We can also infer, that the train from Dunhill running towards Stanton had begun it's journey at 10:40 AM and took 75 minutes to cover 1/4th of the total distance by 11:55 AM.
At constant speed, the train from Dunhill will take another 75 x 3 = 225 minutes from 11:55 AM to cover 3/4th of the distance to reach Stanton, i.e. the train will reach Stanton by
3:40 PM.
Correct answer is
E.