8. (a) Let C be a counterclocwise boundary of a tri- angle with vertices (0,0), (1,2) and (0, 2). Using Green's theorem, calculate 4r ydr +2dy. C 9. Let C be a counterclockwise boundary of a square formed by the lines z = 0, I = 2, y = 0 and y = 2. %3D %3D Using Green's theorem, calculate (z - y)dr +2rydy.