This problem should be disabled immediately.
Solution given is 1...Rxf1+ leading to a winning King and one pawn versus King and one pawn ending. But 1...Kc5 and 1...Kd5 are completely winning too. They lead either to exactly the same winning pawn ending, or in 3 moves Black will have rook, knight, and pawn against rook, which a 1400 player could win against a Grandmaster.
I lost rating points on this, playing 1...Kc5. Grrr
