A quarterback is standing stationary waiting to make a pass when he is tackled from behind by a linebacker moving at 4.75 m/s.

A quarterback is standing stationary waiting to make a pass when he is tackled from behind by a linebacker moving at 4.75 m/s. The linebacker holds onto the quarterback and they move together in the same direction as the linebacker was moving, at 2.60 m/s. If the linebacker's mass is 159 kg, what is the quarterback's mass?