SnotNose: Alive. needed to avoid a ko. If at , Black can squeeze for life.
Why not at ? If the shape is alive even with fewer outside liberties, shouldn't the potential of B playing at be kept for later (ie making gote)?
unkx80: Suppose the White wall is changed as shown. Playing at a gives 5 points, while playing at b gives 4 points. Maybe that's the intention of the problem author?
SnotNose: Alive, a and b are miai. No ko when this shape is not in the corner.
SnotNose: Alive. Same as previous problem.