Answer:
4.254320865115cm or simplied 4.25cm
Explanation:
From the ideal gas equation,

where n is number of moles, R is Universal gas constant, P is pressure, V is volume, and T is temperature of the gas.
The pressure and volume are inversely proportional to each other at constant temperature and number of moles.
Hence, on decreasing the pressure, the volume will increase.
As the hiker reaches a height of a mountain, the pressure would decrease which results in the reestablishment of equilibrium between gas molecules thus resulting in pushing of bag outwards.
Hence, the bag will expand as the hiker reaches the top of the mountain.
The film which you called it is photographic film and it is strip like sheet and it's surface is clrear and transparent plastic which is coated on
two sided one side is with gelatin emulsion consists microscopic small light-sensor which is actually very sensitive in nature silver halides crystals. The size shape and other characters of the crystals gives the sensitivity,contrast of different colors combination ,and resolution of the films.