Tension in the cable is equal to the force due to action of acceleration due to gravity plus the force for accelerating the elevator further by 1.4 m/s.
Thus tension in cable =
(Mass of elevator)*(accelaration due to gravity + upward accelaeartion of elevator)
= 240*(9.8 + 1.4) = 240*11.2 = 2688 N
Answer: Tension in cable is 2688 N