Stokes' Theorem Question Multivariable Calc?

Does anybody have an explanation to this problem? F(x,y,z)=x^2e^yzi+y^2e^xzj+z^2e^xyk S is the hemisphere x^2+y^2+z^2=4, z>=0, oriented upward. Use Stokes theorem to evaluate the double integral curlF * ds