In a game of football, a receiver is standing still, having just caught a pass. Before he can move, a tackler, running at the velocity of +4.9 m/s, grabs him. The tackler holds onto the receiver, and the two moves off altogether having velocity of +3.5 m/s. The mass of the tackler is 130 kg. Supposing that momentum is conserved, determine the mass of the receiver.