Twenty years ago, Dmitri consumed bread which cost him 10 kopecks a loaf, and potatoes which cost him 13 kopeks a sack. With his income of 366, he bought 11 loafs of bread, and 12 sacks of potatoes. Today he has income of 510, but bread now costs him 20 kopeks a loaf and potatoes cost him 20 kopeks a sack. Assuming his preferences have not changed, when was he better off? Explain