A point charge q moves from point P to point S along the path PQRS In a uniform electric field E→ pointing parallel to the positive direction of the x-axis.. The coordinates of the points P, Q, R and S are (a, b,0); (2a,0,0),(a, -b, 0) and (0,0,0) respectively. The work done by the field in the above process is given by the expression