Let K = [m,n]X[p,q][r,s] be a cuboid with straight edges. and let f: [m,n] - R g : [p,q] - R h : [r,s] - IR be three integrable functions. Show that if at least one of those functions has a null integral in R, then: SO" F(x)g(x)h(z)dv=0 K