= Solution
For red-to-yellow conversion, subtract the red values from the yellow values:
$$
\Delta_rH^\circ=(-90.2)-(-90.7)=+0.5\,\mathrm{kJ\,mol^{-1}},\qquad
\Delta_rS^\circ=73.0-72.0=+1.0\,\mathrm{J\,K^{-1}\,mol^{-1}}.
$$
Hence
$$
\boxed{\Delta_rG^\circ(T)=500-T\quad\mathrm{J\,mol^{-1}},\qquad\Delta_rG^\circ(298\,\mathrm K)=+202\,\mathrm{J\,mol^{-1}}\simeq+0.20\,\mathrm{kJ\,mol^{-1}}.}
$$
The positive value makes the red form the lower-<Gibbs free energy> form at 298 K within the supplied bulk-phase model. The calculation uses 298 K as the conventional reference <temperature>; the paper supplies no separate numerical <temperature> for this subpart. Keeping <enthalpy> and <entropy> in the same energy units is essential.
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