6. (a) Consider the line integral (2x+y) dx + 2y dy, where C is part of the ellipse 92 + 16y² = 144 from the point (0,3) to the point (0,-3). Plot the curve C and evaluate the line integral. (b) Consider the surface integral r(u, v) =<ucos v, usin v,v>, integral. =√1+ 2+ y² dS where S is the surface of the helicoid 0≤u≤1, 0 ≤2. Plot the surface S and evaluate the surface