The engine E pulls wagons A, B and C up to track t5 where it uncouples them. 
The engine then continues on to t7, from where it reverses down to t4, goes forward over the bridge, backs into the three wagons A, B, C on t5 and pushes them up onto t7.
Wagon C is uncoupled and left on t7. Wagons A and B are pulled down to t6 and both are uncoupled on that track.

The engine then forwards down to t4, reverses over the bridge, forwards to t7 and pulls C down to t5 where it is uncoupled. The engine then reverses down to t1, goes forward across the bridge and backs up into A and B, pushing them onto t7. The engine uncouples from the wagons and forwards down t6 to t4, reverses over the bridge, forwards up to t5 and pushes C onto A and B.

The wagons are now coupled in the required order (CAB) on t7 but the engine is facing the wrong way. The engine reverses down to t4, forwards over the bridge, backs up into the three wagons on t7 and pulls them down to t1.
The configuration will now be as shown in fig.2.

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