In an​ economy, the desired consumption and investment functions are given​ by, CSuperscript d ​= 5000 ​ 0.20Y - 5000r ISuperscript d ​= 2400 - 4500r where Y is output and r is the real interest rate. Government​ purchases, G​ = 2000. Part 2 Determine the equation for the national saving function to show how desired national​ saving, SSuperscript d​, depends on r and Y.