From time 0 to l1. person A spend money at a rate that is (increasing, decreasing, 0, constant but not 0), and Person B spends money at a rate that is (increasing, decreasing, 0, constant but not 0). From time l1 to l2, Person A spends money at a rate that is(increasing, decreasing, 0, content but not 0). and Person B spends money at a rate that is (increase, decreasing, 0,constant but not 0)