B4 (blue four) cuts to the open side, in an attempt to get free
At this relative distance, he should be able to realise that he should not cut any further if he is unable to get free on the open side. In the effort to clear, he plants to the breakside.
B1 (the thrower), seeing that B4 could not get clear and is planting to the breakside, makes an attempt to breakmark.
The pair B4 and R4 takes the disc and goes to the back of their own stack.
B5 should have another disc (since this drill requires multiple discs). The drill proceeds the same way as above, in the opposite direction.