20. A force ˆ ˆ F k yi xj =- + ( ), where k is a constant, acts on
a particle moving in the x-y plane. Starting from the
origin, the particle is taken from the origin (0, 0) to the
point (a, 0) and then from the point (a, 0) to the point (a,
a). The total work done by the forc
F on the particle is
*