This given figure as in below demonstrates how consumption of goods A, B, C and D varies like a family’s income changes. Since income rises, the income elasticity of demand is positive and increasing for: (w) good A. (x) good B (y) good C. (z) good D.
![945_Income Elasticity of Demand.png](https://secure.tutorsglobe.com/CMSImages/945_Income%20Elasticity%20of%20Demand.png)
Can anybody suggest me the proper explanation for given problem regarding Economics generally?