A 10.0-L gas tank containing 3.20 moles of ideal He gas at 20.0°C is placed inside a completely evacuated, insulated bell jar of volume 35.0 L. A small hole in the tank allows the He to leak out into the jar until the gas reaches a final equilibrium state with no more leakage. 

(a) What is the change in entropy of this system due to the leaking of the gas? 

(b) Is the process reversible or irreversible? How do you know