A mountaineer is climbing a very tall mountain. She has bottled oxygen (oxygen gas in a rigid, metal cylinder) with her, and she breathes the oxygen on the ascent. At the summit, she stops breathing the bottled oxygen and descends safely to the base of the mountain. The temperature on the summit is –15°C, and the temperature at the base is 20°C. Describe how the change in temperature and the change in the amount of gas in the oxygen cylinder affect the pressure of the gas inside the cylinder during the ascent and descent of the mountain