Train synchronize relativity problem

[ryan3]

Homework Statement

Consider four clocks at different locations in train: A and D at two ends, B and C midway between the center and A and D respectively. How can a people standing at the center of the train synchronize all four clocks with a mirror M which he can install beforehand at arbitrary positions inside the train?

 

[ryan3]

any comments/ idea?

I have been thinking this for a day but have no direction...

thanks...