We have in this problem four unknowns to be determined, K, X, Y and Z. In general, one has much more than four observed galaxies, and the resulting system of equations turns out to be overdetermined (more equations than the number of unknowns). This is a rather common situation in astrophysics. For example, a binary stellar system can be spectroscopically observed in many orbital phases yielding a set of observations much larger than the number of unknowns of the problem (orbital inclination and eccentricity, mass ratio, etc.)