Question: two moles of an ideal gas are contained under 50...

Two moles of an ideal gas are contained under 50 atm and 300K. After removal of the stopper 1, the gas expands adiabatically to stopper 2. The external pressure of the gas is 20 atm.  

1) Calculate the work performed by the gas

2) Calculate the entropy change of the gas

3) Calculate the entropy change of the environment