An object is under the force F = (k1*x) i - (k2*y) j. Calculate the work done by this force when the object:
a) moves on the x-axis from the origin to the point (a,0), and then goes from (a,0) until (a,b) parallel to the y-axis;
b) moves from the origin to the point (0,b), and then goes from (0,b) until (a,b) parallel to the x-axis.