Find the circulation and flux of the field F = - 4xi - 4yj around and across the closed semicircular path that consists of the semicircular arch r, (t) = (a cost)i + (a sin t)j, Ostsn, followed by the line segment r2 (t) = ti, - asta. . . . The circulation is (Type an exact answer, using it as needed.) The flux is. (Type an exact answer, using it as needed.)