By the people for the people
I would say an investigation is a part-by-part scrutiny of a given problem. An investigation is examining a problem as to for example, what happened, how did it happen, when and why and re the consequences.
The correct answer is a Credit Union.
Credit Unions are able to charge lower rates than a bank because of their structure. Banks are set up as a for-profit business, so they charge more in order to make themselves more profitable. Credit Unions are set up like cooperatives where the customers own them, or like a non-profit organization. This allows Credit Unions to charge lower rates. Additionally, the Credit Unions normally distributes the profit back to the customer.