Školjka

%V0 Consider a convex polyhaedron without parallel edges and without an edge parallel to any face other than the two faces adjacent to it. Call a pair of points of the polyhaedron antipodal if there exist two parallel planes passing through these points and such that the polyhaedron is contained between these planes. Let $A$ be the number of antipodal pairs of vertices, and let $B$ be the number of antipodal pairs of midpoint edges. Determine the difference $A-B$ in terms of the numbers of vertices, edges, and faces.