Why does Mother think that Mrs. Ogilvie's fourth son will want or need marry the daughter of a business owner?

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Read Fever, 1793, by Laurie Halse Anderson

Why does Mother think that Mrs. Ogilvie's fourth son will want or need marry the daughter of a business owner?

Answer:

Lucille Cook (Mother) claims that Edward Ogilvie being the youngest of his brothers could find marrying a woman with an established business, such as their coffeehouse, as "the best he can hope for."

Explanation:

Matilda's mother wants her to marry Edward, Mrs. Pernilla Ogilvie's son, although she doesn't want to marry the rich aristocrat. When Mrs. Ogilvie, invites them to have tea at her house, Lucille sees an opportunity to make the marriage happen.