State why argon is used in the light bulb. explain your answer in terms of the electronic structure of an argon atom.

Hi I need Help with this :
A swimming pool has an inlet pipe that can fill the empty pool in 12 hours with the drain is closed and the inlet pipe is closed the drain can empty the full pool in 20 hours. When the pool is empty how long will it take the inlet pipe to fill the pool drain if it is left open ?

The air is going to come out because of the low pressure.