Solution :
Given :
Reserve requirement = 20 %
Leroy receives = $1000
So the bank can hold [tex]$20\%$[/tex] of [tex]$1000$[/tex] as a reserve. That means, it is has to hold [tex]$200$[/tex] as reserves. So it can lend the remaining [tex]$800$[/tex].
[tex]$\text{Multiplier} = \frac{1}{\text{required reserve ratio}}$[/tex]
[tex]$=\frac{1}{0.2}$[/tex]
= 5
Thus, the maximum expansion of money supply = 800 x 5
= 4000