A force \[F=-K(yi+xj)\] (where K is a positive constant) acts on a particle moving in the xy-plane. Starting from the origin, the particle is taken along the positive x-axis to the point (a, 0) and then parallel to the y-axis to the point (a, a). The total work done by the force F on the particles is [IIT 1998]

• A.             \[-2K{{a}^{2}}\]
• B.               \[2K{{a}^{2}}\]
• C.             \[-K{{a}^{2}}\]       
• D.             \[K{{a}^{2}}\]