Judy's Marshallian demand for oranges is I^0.7/[2p_o(p_a+3)^0.4] where p_a is the price of apples, p_o is the price of oranges, and I is Judy's income. Suppose I = 100, p_a = 2 and p_o = 1.

1. Find and interpret the income elasticity for the demand for oranges. Are oranges an inferior or normal good?
2. Find the own price elasticity of demand for oranges. Discuss how the price elasticity varies with p_o
3. Find the cross price elasticity for oranges. Are oranges and apples gross substitutes or gross complements?