# How to interpret income elasticity of demand

My question:

Income elasticity of demand for apple is $\gamma$. Cross elasticity of demand between apple quantity and orange price is $\psi$, What is the impact on apple's revenue if consumers' income increase by x% and orange price fall by y%?

What I think the answer is?: Am I right I say that revenue would increase for the first instance (income) and the revenue will fall for the second instance. However, how would I know the percentage of revenue increase in the first instances and fall in the second instances?