Margaret has a monthly amount of her income of $20 devoted to purchasing two items: nail polish and eyeliner. The first bottle of nail polish gives 20 units of utility and the second gives 12 units of utility. The first eyeliner gives 40 units of utility and the second gives 10 units of utility. The price of nail polish is $5 and the price of eyeliner is $9. The 12 units of utility is described as the of consuming the second bottle of nail polish. Adding 20 units and 12 units = 32 units of utility. This is described as the of two bottles of nail polish. For both nail polish and eyeliner, because the second unit yielded less utility than the first (and we expect additional units to yield less additional utility), these products conform to the . Based on the prices of the products and using the budget of $20, it is possible to graph the . If the combination of 2 nail polish and 1 eyeliner gave 72 total utility and the combination of 3 eyeliner and 0.5 nail polish gave 72 total utility as well, those two combinations of goods could be plotted on a(n)