Complexes (ML5) of metals Ni and Fe have ideal square pyramidal and trigonal bipyramidal geometries, respectively. The sum of the 90°, 120° and 180° L-M-L angles in the two complexes is____

ML5 with Square pyramid.                                                         Contains eight 90° angle and two diagonal 180° angles (total=10).         ML5 with TBP structure.                              Contains six 90° and three 120° and one 180°. So total = 10.          Sum in both = 10 + 10 = 20.