In the divide-and-conquer convex hull algorithm, we know how to find the upper tangent and the lower tangent of two disjoint convex polygons. There are four possible tangents between two disjoint convex polygons. A cross-tangent is a tangent line that has one polygon below it and the other one above it. Let A and B be disjoint convex polygons, each with n vertices. Describe an O(n) time algorithm to find one of the cross-tangents of A and B.