If S is the surface of the sphere x2 + y2 + z2 = a2, then the value of
\(\mathop \int\!\!\!\int \limits_S \left( {x + z} \right)dydz + \left( {y + z} \right)dzdx + \left( {x + y} \right)dxdy\) is1
\(\frac{4}{3}\pi {a^3}\)
2
\(\frac{8}{3}\pi {a^3}\)
3
\(\frac{2}{3}\pi {a^3}\)
4
\(\frac{1}{3}\pi {a^3}\)