What checks can White give with his queen? Four: Qa4, Qb5, Qe6, and Qxf7. Two of those—Qa4 and Qb5—also attack the black bishop. The bishop is protected, so naturally you look for an exchange that would leave a loose piece on a6. White can go after the bishop with his rook; after 1. RxB, RxR, White has a good loose target to pair with his check of the king. He plays Qb5+ and takes the rook, again netting a piece.