Hello all!

I can not solve a difficult task from the vector analysis:

*Using Stokes formula, calculate the curvilinear integral of the second kind:* $\displaystyle I = \int\limits_{OA} {yzdx + 3xzdy + 2xydz,}$

*where* $\displaystyle OA = OB \cup BC \cup CA$, curve $\displaystyle x = t\cos t,{\text{ }}y = t\sin t,{\text{ }}z = {t^2},{\text{ }}0 \leqslant t \leqslant 2\pi ,{\text{ }}O = \left( {0,0,0} \right),{\text{ }}A = \left( {2\pi ,0,4{\pi ^2}} \right).$

I have two carefully (I thought) addressed this problem

, but my answer is clearly not the same as the right one.