A 100% stacked bar chart displays the electricity generation mix (Coal, Hydro, and Solar) for three regions, $R_1, R_2,$ and $R_3$:

• For $R_1$, the generation composition is Coal ($55\%$), Hydro ($25\%$), and Solar ($20\%$). The total generation of $R_1$ is $400\text{ TWh}$.
• For $R_2$, the generation composition is Coal ($30\%$), Hydro ($50\%$), and Solar ($20\%$). The total generation of $R_2$ is $600\text{ TWh}$.
• For $R_3$, the generation composition is Coal ($40\%$), Hydro ($40\%$), and Solar ($20\%$). The total generation of $R_3$ is $500\text{ TWh}$.

If these three regions are combined, what is the overall percentage contribution of Hydro power to the total pooled electricity generation?