In the diagram, D is the demand curve for an agricultural commodity and ${S_1}$ is the initial supply curve. A good harvest causes the supply curve to shift to ${S_2}$.
By how much will the demand curve have to shift to leave farm incomes unchanged?
1 )
500 tonnes at all prices
1000 tonnes at all prices
3 )
2000 tonnes at all prices
4 )
4000 tonnes at all prices
