Forced Material II
In a game I might not take the rook, I would probably go for checkmate, but either way, black wins.
Also, why is the c3 sack necessary, it looks like it just hurts white by dropping a pawn and a tempo.
I'm sorry, but I don't see this as much of a puzzle. White is already two pieces down, with a third (the a3 Knight) free for the taking by black. The move Pc3 throws away the pawn AND the a1 rook. Why not just play 2. Kf2, rather than throw away additional material? Not that it matters, but where is the "forced" material loss?