Two moles of an ideal gas are contained under $50$atm and

$300K.$ After remove the stopper $1,$ the gas expands adiabatically

to stopper $2.$ The external pressure is $10$atm during expansion.

The final pressure of the gas is $20$atm. Calculate $(1)$ the work

done by the gas, $(2)$ the entropy change of the gas and $(3)$ the

entropy change of the environment.