Question 5 15 points National Saving Ignore inventory changes and government gross investment for this question. a. State the equations of private saving and public saving. [Derivation not required.] b. State the relation between national saving and national investment in a closed economy. [Derivation not required.] c. State the relation between national saving and national investment in an open economy. [Derivation not required.] d. Suppose one country started with a trade surplus with the rest of the world in 2021. That is N X 2021 > 0. During 2022, its . national saving increases ($2022 > $2021) . national investment also increases (12022 > [2021) Based on the situation above, explain: . what could have happened during 2022 to its net exports, N X2022; which one of N X2021 and N X2022 is greater; . if the country runs a trade deficit, trade surplus, or zero trade balance during 2022