part-a: what is the income effect? (5 pts) part-b: what is the substitution effect? (5 pts) part-c: suppose there are two goods which are substitutes and the price for one of the goods increases. how does the substitution and effect impact the quantity demanded of the good, which gets more expensive? can we say for certain what will happen to the quantity demanded for this good? how does the substitution and effect impact the quantity demanded of the good, whose price remains the same? can we say for certain what will happen to the quantity demanded for this good? (10 pts)