For each of the following, (i) give the systematic name of the compound and specify the oxidation state of the transi-tion metal, (ii) draw a crystal field energy-level diagram and assign the d electrons to orbitals, (iii) indicate whether the complex is high-spin or low-spin (for d4 - d7 complexes), and (iv) specify the number of unpaired electrons.

(a) (NH4)[Cr(H2O)6](SO4)2