When A and B are pulling on the rope the tension in the rope is the sum of the forces with which each of A and B is pulling the rope. To be able to pull the rope towards himself the force that either A or B has to apply should be equal to the tension in the rope.
Here we are given that the tension in the rope is 1956 N. A is able to pull B by 2.8 m.
The work done by A in doing so is equal to force*distance.
Using the values given we have work = force*distance = 1956*2.8 = 5476.8 J
The required value of the work done by A is 5476.8 J.