It is required an infinite work. The additional electron will never reach the origin.
In fact, assuming the additional electron is coming from the positive direction, as it approaches x=+1.00 m it will become closer and closer to the electron located at x=+1.00 m. However, the electrostatic force between the two electrons (which is repulsive) will become infinite when the second electron reaches x=+1.00 m, because the distance d between the two electrons is zero:
[tex]F=k_e \frac{q_e q_e}{d^2} [/tex]
So, in order for the additional electron to cross this point, it is required an infinite amount of work, which is impossible.
