The Nile Basin countries, including Ethiopia and Egypt, have engaged in discussions and negotiations under the framework of the Nile Basin Initiative $($NBI$),$ aiming to promote cooperation, joint management, and sustainable development of the Abay River's resources.

a$)$ Can you identify a country that consistently adopts a zero$-$sum game approach in its use over the river? Please provide an explanation for your answer.

b$)$ Can you identify a country that actively pursues win$-$win solutions in its use over the river? Please explain your answer.