Prepositional logic question, help!!?

Put the following argument in propositional form, and prove its validity.

If the floating feeling of peace that people experience when theyre near death is due to being near God in Heaven, then only Heaven-bound people should experience it. If that feeling is due to oxygen deprivation, then it should happen not only when people are near death but also when theyre at high altitudes. Bad people experience the floating feeling of peace when theyre near death, as do people at high altitudes. Therefore, the feeling is not due to being near God in Heaven.

 

The part that I m having trouble putting in prepositional form is this part: If that feeling is due to oxygen deprivation, then it should happen not only when people are near death but also when theyre at high altitudes.

not only is "or"....

 

If that feeling is due to oxygen deprivation then it should happen when people are near death OR when they're at high altitudes.