The complication in the 6th mission of the series is that now there might be needed more than one light bulb to illuminate a room. And this is the 5th argument of the function - how many light bulbs are needed to illuminate the room.
For example, if you need 3 bulbs to illuminate a room, then we don’t count the time when there were only 2 bulbs or only one. If the last argument of the function is not passed, then one light bulb is enough to illuminate the room.
The task is still the same - to find out how long the room was lit (in this task, we can say - sufficiently lit).
... Five arguments and only the first one is required. The first one is an array of Date objects (instead of Date object there can be an array of two Date and number), the second and the third ones are the Date objects or undefined. The forth argument - integer - how long the lamp can work. The 5th argument is a positive non-zero int.