Hello!
The partial pressure of helium to keep the partial pressure of oxygen at 0,21 atm in a scuba-diver tank is
8,09 atmTo solve this question, we can use the
Dalton's Law, which states that the total pressure in a container with a mixture of gases is the sum of the partial pressures o each individual gas. For the case of this mixture the Dalton's Law is as follows:

In this equation, we need to clear for PHe, knowing that the PO₂ should be 0,21 atm, to find the required pressure of Helium:

Have a nice day!
The answer is "Location E, because Earth's axis is tilted towards the sun" :D
If an electron moves up from the first orbit to the higher energy levels, energy will be absorbed by the electron itself and no emission line produced.
But if it moves from the orbits 6,5,4 and 3 to orbit 2, energy will be released by the electron and different emission lines wll be produced.