The amount of energy required to split the double strand DNA into two single strands is $\_\_\_\_$ kcalmol ${ }^{-1}$.
[Given: Average energy per H-bond for A-T base pair $=1.0 \mathrm{kcalmol}^{-1}, \mathrm{G}-\mathrm{C}$ base pair $=1.5 \mathrm{kcalmol}^{-1}$, and $\mathrm{A}-\mathrm{U}$ base pair $=1.25 \mathrm{kcalmol}^{-1}$. Ignore electrostatic repulsion between the phosphate groups.]
