The fed regulates the money supply using basic tools of operation.

Federal make different of the reserves of commercial banks, mostly through sales and purchases of government bonds. A federal funds rate reduction that is caused by monetary policy will lower the prime interest rate. If the Federal Reserve System will buy government securities from the public and commercial banks, it will be easy  to get loans at commercial banks. 

It will take 6 years and 183 days to cover for the investment.

Explanation:

Giving the following information:

Cash flow:

Cf1 trough 3= 100

Cf4 trough 8= 75

Initial investment= 475

The payback period is the time required to recover the initial investment.

Year 1= 100 - 475= -375

Year 2= 100 - 375= -275

Year 3= 100 - 275= -175

Year 4= 75 - 175= -100

Year 5= 75 - 100= -25

Year 6= 75 - 25= 50

To be more accurate:

(25/50)*365= 183

It will take 6 years and 183 days to cover for the investment.