If the legal reserve requirement ration is 20% and banks desire zero excess reserves, and if people deposit

$5 billion from currency hoards into checking accounts, then, after two rounds of new lending by banks

the initial $5 billion increase in demand deposits could expand the money supply by:

(a)$5 billion. (b)$4 billion. (c)$1 billion. (d)$7.2 billion. (e)$2.2 billion.