$24 \mathrm{kcal} \mathrm{mol}^{-1}$

$12 \mathrm{kcal} \mathrm{mol}^{-1}$

$24 \mathrm{cal} \mathrm{mol}^{-1}$

$12 \mathrm{cal} \mathrm{mol}^{-1}$

linear with +ve slope and non zero +ve intercept

linear with -ve slope and non zero +ve intercept

linear with -ve slope and zero intercept

linear with $+v e$ slope and zero intercept