Two blocks of masses 20kg and 8kg are connected together by…

Two blocks of masses 20kg and 8kg are connected together by a light string and rest on a frictionless surface.  Attached to the 8kg mass is a second light string, which a person uses to pull both blocks horizontally.  If the 2 block system accelerates at 0.5 m/s^2, what is the tension in the second light string?