Figure[Black to move]

Notice that while White’s position is slightly different here—his king is tucked into the corner—Black’s resources are arranged the same way as in the last position: he has a queen and rook trained on the square in front of White’s rook, and another rook (this time on the b-file) ready to drop to the back rank once the file is cleared. So play proceeds the same way: Black starts with Qxg2+; White is required to play RxQ; Black plays Rb1+, forcing White’s rook to interpose back on g1; and then Black mates with RxR.