Correct answer: Ra81...b6 2.B:b6# 1...Rc3/Rc2/Rc1/Rc5/Rc6/Rc7/Rc8 2.Q:b4# 1.R:b7?? (2.Bb6#) 1...Rc5/Rc6 2.Q:b4# but 1...Bc5! 1
