if MPC is 0.9 and increase in investment is Rs. 100 crore , find out increase in national income

in an economy marginal propensity to save is 0.2 investment increase by Rs. 1,000 crore , calculate total increase in national income .

in an economy investment is increased by Rs. 300 crore .If MPC is 2/3 , calculate increase in national income .

Suppose marginal propensity to consume is 0.8. How much increase in investment is required to increase naitonal income by 2000 crore?Calculate