Expansion work for dry ice?

A 22.6 g quantity of dry ice (solid carbon dioxide) is allowed to sublime (evaporate) in an apparatus like the one shown in Figure 6.5. Calculate the expansion work done against a constant external pressure of 0.969 atm and at a constant temperature of 26�C. ume that the initial volume of dry ice is negligible and that CO2 behaves like an ideal gas.