Rectangular six with leg in the corner
Black-to-move plays b or c; I have not worked out what ko threats those leave behind. After either of those moves, the only other thing left in the corner is the (double-)gote hane-connect.
This is a shape between a walkie talkie seven and a rectangular six in the corner. If White has sente, the vital point in the former is a, in case of no outside liberties, and in the latter is b or c depending on whether thereare still outside liberties.
So which is it here?