From what I know banks don’t have to borrow money from other banks to lend it. There is insane mechanism underneath - banks can actually lend x times more money that they currently have, without borrowing it from anywhere. This is a way to "print" digital money from the air.

Also instead of presenting two lines, wouldn’t it be better to divide these values like f3(x)=f1(x)/f2(x)? We should get something like f3(x)=1, right? It this the case?