a queston on the back of a matchbox??

an old steam train travels from Aton to Bton at 50mph, but from Bton to Aton at 75mph, as the journey involves a steep gradient. It takes the engine two hours longer to do the uphil journey than it does to return on the downhill stretch.

How far apart are Aton and Bton?

if you want the answer you have to SAE it i can't be bothered - but would like to know. it would settle a little argument


Cheers

Daniel