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Another kind of integration

Calculate the integral of the following differential form: $w(x,y,z) = \frac{ x \space dy \wedge dz + y \space dz \wedge dx +z \space dx \wedge dy}{(x^2 + y^2 + z^2)^{\frac{3}{2}}}$ over the surface of the sphere with center $$(0, 0, 0)$$ and radius $$r$$, oriented with the outer normal.