Explore the following: https://apps.newyorkfed.org/markets/autorates/fed%20funds
What is the Fed Funds rate and what happened to the Fed Funds rate in the days following the collapse of Bear Stearns and then of Lehman Brothers?
What determines the level of the Fed Funds Rate? What is the difference between the effective fed funds rate and the target fed funds rate?
https://www.newyorkfed.org/aboutthefed/fedpoint/fed15.html