(1 + c)/(r + e + c). The money multiplier (also called the credit multiplier or the deposit multiplier) is a measure of the extent to which the creation of money in the banking system causes the growth in the money supply to exceed growth in the monetary base.
A buzzing light switch could mean the fixture is wearing out, causing an arc of electricity behind the wall plate. If this is the case, the potential for an electrical fire may exist.
Fluorescent lights sometimes buzz, flicker or hum. This is not something that has to stay the same or be replaced with a whole new light or with a phone call to an electrician. It just means being careful and finding out what the source of trouble is.