需求收入弹性

def solve(____):
    elasticity = quantity_change / income_change
    if elasticity > ____:
        good_type = "____"
    elif elasticity > ____:
        good_type = "____"
    else:
        good_type = "____"
    return {"____": income_change, "____": quantity_change, "____": elasticity, "____": good_type}