Using crystal field theory, sketch the energy-level diagram for the d orbitals in an octahedral field; then

Question:

Using crystal field theory, sketch the energy-level diagram for the d orbitals in an octahedral field; then fill in the electrons for the metal ion in each of the following complexes. How many unpaired electrons are there in each case?
a. [ZrCl6]4–
b. [OsCl6]2– (low-spin)
c. [MnCl6]4– (high-spin)