C = 100 + 0.4 Y is the Consumption Function of an economy where C is Consumption Expenditure and Y is National Income. Investment expenditure is 1,100. Calculate
(i) Equilibrium level of National Income.
(ii) Consumption expenditure at equilibrium level of national income.

(1) Calculation of equilibrium level of national income:
Given, Consumption Function (C) =100+0.4Y
Investment expenditure (I) = 1,100
At equilibrium level AD= AS OR y= C+I 
By substituting values
Y=100+0.4Y + 1100
Y – 0.4Y = 1200
0.6Y=1200
OR Y =2000
Hence equilibrium level of national income = 2000

(2) Calculation of Consumption expenditure at equilibrium level of national income:
C= 100+0.4Y (Given)
Equilibrium level of national income = 2000
C= 100+0.4 *2000
C = 100+ 800
Therefore Consumption expenditure (C) at equilibrium level of national income (2000) = 900