I think it’s as simple as Rc8+! Rxc8 b7+. Now if Ka7 then bxc8(Q) with mate next move. If instead Kb8 then Kb6 Rc6+ (forced otherwise a7#) Kxc6, Ka7 (forced otherwise Kb6 and a7#) Kc7 Kxa6 b8(Q) and the Q wins easily.
1. b7+? as suggested is not the right solution, because of f.e. the following line: 1. … Ka7! 2. Rc8 Rc2+ 3. Kb5 Rb2+ 4. Kc6 Rb6+ 5. Kc7 Kxa6 6. Ra8+ Kb5 7. b8Q Rxb8 8. Rxb8+ Kc4 and the free pawns of black are decisive…
I think it’s as simple as Rc8+! Rxc8 b7+. Now if Ka7 then bxc8(Q) with mate next move. If instead Kb8 then Kb6 Rc6+ (forced otherwise a7#) Kxc6, Ka7 (forced otherwise Kb6 and a7#) Kc7 Kxa6 b8(Q) and the Q wins easily.
1.Rc8+ R:c8
2. b7+ Kb8
3. Kb6 looks like a forced win to me
Its a win for white. Rc8+, Rxc8 (forced), b7+ and it shd be easy from there.
-B
I think white wins:
1. b7+ Kb8 (1…Ka7 2.Rc8 wins with double threat of b8=Q# and Ra8#)
2. Rc8+ Rxc8
3. Kb6! (threatens 4.a7#) Rc6+
4. Kxc6 Ka7 (4…d2 5.Kb6 and 6.a7#)
5. Kc7 winning
1. Rc8+ Rxc8
2. b7+ Kb8
(or 2. … Ka7 3. bxc8Q d2 4. Qb7#
3. Kb6 Rc6+
(or f.e. 3. … d2 4. a7#)
4. Kxc6 Ka7
(or f.e. 4. … d2 5. Kb6 d1Q 6. a7#)
5. Kc7 Kxa6
(or f.e. d2 6. b8Q+ Kxa6 7. Qb6#)
6. b8Q Ka5
7. Qb3 d2
8. Kc6 d1Q
9. Qb5#
White wins.
1) Rc8+ Rxc8
2) b7+ Kb8 (Ka7 loses)
3) Kb6 Rc6+ (only move to prevent a7)
4) Kxc6 Ka7 (d2 and White plays 5) Kb6 threatening mate)
5) Kc7 (followed by b8Q)
1. b7+? as suggested is not the right solution, because of f.e. the following line:
1. … Ka7!
2. Rc8 Rc2+
3. Kb5 Rb2+
4. Kc6 Rb6+
5. Kc7 Kxa6
6. Ra8+ Kb5
7. b8Q Rxb8
8. Rxb8+ Kc4
and the free pawns of black are decisive…