Different roles of banks, government, central banks, in controlling the business cycle.

Bank is a financial intermediary that uses liquid assets in the form of bank deposits to finance the illiquid investments of borrowers. Banks can create liquidity because it isn’t necessary for a bank to keep all of the funds deposited with it in the form of highly liquid assets. Except in the case of a bank run—which we’ll get to shortly—all of a bank’s depositors won’t want to withdraw their funds at the same time. So a bank can provide its depositors with liquid assets yet still invest much of the depositors’ funds in illiquid assets, such as mortgages and business loans.

2.How money is created by banks through checking accounts and the role of the money multiplier.

Multiplier
The expansion of a country's money supply that results from banks being able to lend. The size of the multiplier effect depends on the percentage of deposits that banks are required to hold as reserves. In other words, it is money used to create more money and is calculated by dividing total bank deposits by the reserve requirement.

The multiplier effect depends on the set reserve requirement. So, to calculate the impact of the multiplier effect on the money supply, we start with the amount banks initially take in through deposits and divide this by the reserve ratio. If, for example, the reserve requirement is 20%, for every $100 a customer deposits into a bank, $20 must be kept in reserve. However, the remaining $80 can be loaned out to other bank customers. This $80 is then deposited by these customers into another bank, which in turn must also keep 20%, or $16, in reserve but can lend out the remaining $64. This cycle continues - as more people deposit money and more banks continue lending it - until finally the $100 initially deposited creates a total of $500 ($100 / 0.2) in deposits.