On page 97, the author talks about how much money Marta & Esperanza's families have. How does the author use this part of their backgrounds to develop the characters of Marta and Esperanza? chapter 6

In context, Esperanza's family is ridiculed because they'd been riched, as evidence in Marta's calling Esperanza Cinderella. The two girls come from very different backgrounds, something that is also illustrated through Esperanza's inability to properly execute her chores. She doesn't even know how to sweep properly.