We know that the desired reserve ratio for the banking system is 10%. Assume that the banking system has an excess reserve equal to $4 billion. Further, the currency in circulation equals $450 billion, and the total amount of checkable deposits equals to $900 billion.

Calculate the following:

a) Desired reserves held by the banking system

b) Total reserves held by the banking system

c) Monetary base

d) Total money supply (M1)

e) The money multiplier