Take that, splice it into 15-amp NM, splice that into BX, hook that up to a 20 amp breaker in a box that somehow - don't ask me how, but an electrician has confirmed - has TWO mains - a 60 and a 40 - coming in from the meter. And a 20 amp breaker for a subpanel in an outbuilding workshop wired for 75 amp.
Last time I tried to replace a ceiling light, it took me and a master electrician FOUR HOURS just to figure out how the duplex switches were wired (with a combination of BX and NM, of course).