Rectangular six with leg in the corner
If Black plays b or c, then (other than ko threats) the only 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 (walkie talkie seven) is a, in case of no outside liberties, and in the latter (rectangular six in the corner) is b or c depending on whether there are still outside liberties.
So which is it here?