= Solution
For two independent identical ions at sufficiently high temperature, <Curie's law> gives $\chi T=2(N_A\mu_B^2/3k_B)g^2S(S+1)$. In the cgs units used here, $N_A\mu_B^2/3k_B\simeq0.125\ \mathrm{cm^3\,K\,mol^{-1}}$.
\b[Fe(II), Co(II) and Ni(II) have $S=2$, $3/2$ and 1, respectively.] The corresponding high-spin occupancies, ordered as $(e'',e',a_1')$, are
$$
\boxed{\mathrm{Fe^{II}}:d^6=(3,2,1),\qquad\mathrm{Co^{II}}:d^7=(4,2,1),\qquad\mathrm{Ni^{II}}:d^8=(4,3,1).}
$$
Hund filling puts one electron in each orbital before additional pairing. Spin-only dimer values at $g=2$ would be 6.0, 3.75 and 2.0; the observed larger values anticipate orbital contributions. The <spin> assignments require the chemically appropriate high-spin states, rather than rounding the measured $\chi T$ directly to a spin-only integer.
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