Helium gas is stored at 20°C in a spherical container of fused silica, which has an inner diameter of 0.20 m and a wall thickness of 2 mm. If the container is charged to an initial pressure of 4 bar,...

Helium gas is stored at 20°C in a spherical container of fused silica, which has an inner diameter of 0.20 m and a wall thickness of 2 mm. If the container is charged to an initial pressure of 4 bar, what is the rate at which this pressure de creases with time?