Chapter 15, Problem 14RE

MATHEMATICAL The $\Delta G{°}^{\prime }$ for the reaction Citrate $\to$ Isocitrare is $+6.64{\text{ kJmol}}^{-1}=+1.59{\text{ kcalmol}}^{-1}$. The $\Delta G{°}^{\prime }$ for the reaction Isocitrate $\to \alpha$-Ketoglutrate is $-267{\text{ kJmol}}^{-1}=-63.9{\text{ kcalmol}}^{-1}$. What is the $\Delta G{°}^{\prime }$ for the conversion of citrate to $\alpha \text{-}$ ketoglutarate? Is that reaction exergonic or endergonic, and why?