(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.
When bulbs are at full brightness, the triac turns on most of the AC wave cycle. At this point, there is not much loss of voltage, so the bulb doesn't buzz. When a lamp is dimmed, the triac effectively switches the lamp on and off 120 times per second.