By applying Stokes theorem, the value of \(\mathop \oint \limits_C \left[ {\left( {x + y} \right)dx + \left( {2x - z} \right)dy + \left( {y + z} \right)dz} \right]\) where C is the boundary of the triangle with vertices (2, 0, 0), (0, 3, 0) and (0, 0, 6), is