InvasionProblem1/B

Correct, according to Yamashita  

The low invasion at the midpoint was played in the actual game and is correct, according to Yamashita. White attached at and Black extended to - a mistake, says Yamashita. He says Black should play as in this and the following diagram.

He provides a refutation for at f to set up a ladder and turn at a instead of making the atari at , but perhaps that would be best set as a separate problem.

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