Today is a beautiful day for a picnic in the mountains, so we seal our peanut butter sandwich in a plastic sandwich bag at the base of the mountain. The approximate volume of the sandwich bag not occupied by the sandwich is 200. mL. The pressure at the base of the mountain is 1.0 atm. If the pressure at the top of the mountain is 0.80 atm, what is the final volume (mL) of gas in our sandwich bag?