What does Esperanza learn when the family meets Carmen on the train?

In Chapter Four, a woman named Carmen offers Esperanza some sweets. Carmen and Mama quickly become friends, exchanging life stories. Mama explains the family's situation to this total stranger, which Esperanza had always believed to be improper. When Carmen departs, she gives Mama two of her chickens in exchange for three of the table coverings Mama had been knitting on the train. Esperanza watches as Carmen exits the train and gives some money to a beggar woman. Miguel explains that people without money have to take care of each other because the rich only help themselves.