Decarboxylation of all six possible forms of diaminobenzoic acids $\mathrm{C}_6 \mathrm{H}_3\left(\mathrm{NH}_2\right)_2 \mathrm{COOH}$ yields three products A, B and C. Three acids give a product ‘A’, two acids gives a product ‘B’ and one acid give a product ‘C’. The melting point of product ‘C’ is