text: here, as the gas is in equilibrium,the pressure exerted by the piston should equal the pressure exerted by the gas..                    Ppiston=mass/area =5g/0.047pa. Use the ideal gas law now..  V=nRT/P and so,area*ht(=V)=nRT/P this implies ht.H=nRT/aP and use your units carefully..i think the answer will be around 203.67502 km