According to the generalizations concerning the composition of equilibrium mixtures, if $K_c > 10^3$, products predominate over reactants, and if $K_c < 10^{-3}$, reactants predominate over products. For reaction (a), $K_c = 5 \times 10^{-39}$, which is very small, meaning reactants predominate. For reaction (b), $K_c = 3.7 \times 10^8$, which is very large, meaning products predominate. For reaction (c), $K_c = 1.8$, which is neither very large nor very small (between $10^{-3}$ and $10^3$), indicating that the reaction mixture will have an appreciable concentration of both reactants and products.