Five Point Mass Gravitational Lenses in a Rhombus as a Soluble Model Giving the Maximum Number of Images

As an extension of four point mass lenses at the vertices of a rhombus, we present five point mass lenses at the center and vertices of a diamond, which constitute, for a source behind the center, a soluble model giving expressions of all the image positions (with the maximum number of images as twenty for five lenses). For a source near the center, all the image positions are obtained in the linear approximation.