One economic problem was that businesses were not as healthy. People started losing money because they had numerous investors and they couldn't find a way to pay them back because they couldn't earn as much as they received in investments which caused investors to lose money in reality which harmed the businesses.
Another is that the consumers were indebted more than it was normal. People were spending more and more money and they in reality didn't have this money earned so the debt started increasing dramatically and when they couldn't pay back the debts the bubble burst and an economic crisis was introduced.
"c. A narrative source" is what a historian would use to get a firsthand account of a past event, since in these sources (which are also primary sources) a person is giving a first-hand account of the event itself.
