How do you know mr bingley's family has his fortune from trade?

Question:

How do you know mr bingley's family has his fortune from trade?

i cant seem to find it in the pride and prejudice book...

Best Answer - Chosen by Asker: "Elizabeth listened in silence, but was not convinced. Their behaviour at the assembly had not been calculated to please in general; and with more quickness of observation and less pliancy of temper than her sister, and with a judgment, too, unassailed by any attention to herself, she was very little disposed to approve them. They were in fact very fine ladies, not deficient in good humour when they were pleased, nor in the power of being agreeable where they chose it; but proud and conceited. They were rather handsome, had been educated in one of the first private seminaries in town, had a fortune of twenty thousand pounds, were in the habit of spending more than they ought, and of associating with people of rank; and were therefore in every respect entitled to think well of themselves, and meanly of others. They were of a respectable family in the north of England; a circumstance more deeply impressed on their memories than that their brother's fortune and their own had been acquired by trade."

Does this help?