## Task 4 - 080734

A cultural hall is being equipped with 21 wall lamps during renovation, each designed for 4 light bulbs. The initially available light bulbs are screwed in randomly. It is then noticed that some wall lamps are equipped with all 4 light bulbs, while twice as many contain only one. Some of the wall lamps have exactly 3 light bulbs, while in half as many, all the light bulbs are missing. In the remaining lamps, there are exactly 2 light bulbs.

The exact number of missing light bulbs is to be determined.
Imagine that from the wall lamps with 4 light bulbs each, 2 are unscrewed from each. This results in exactly as many light bulbs as there are lamps with only 1 light bulb. Therefore, one could screw one light bulb into each of these lamps.

Similarly, imagine that from the lamps with 3 light bulbs, 1 is unscrewed from each. This results in exactly twice as many light bulbs as there are lamps without any light bulbs. Therefore, one could screw 2 light bulbs into each of these lamps. Then, there would be a total of exactly 21 lamps with exactly 2 light bulbs each.

Therefore, exactly 42 more light bulbs are needed to fully equip all the lamps.