The total number of coordination sites
in ethylenediaminetetraacetate (EDTA^4–) is _____.

The oxidation states of iron atoms in compounds (A), (B) and (C), respectively, are x, y and z. The sum of x, y and z is ________.

Na₄[Fe(CN)₅(NOS)]
       (A)

Na₄[FeO₄]
       (B)

[Fe₂(CO)₉]
       (C)

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