4.50 g of methane gas (CH4) occupies 12.7 L at 310 K. Calculate the work, heat, energy and enthalpy change upon: a) expansion by 3.3 L at p=const (isobaric). b) isothermal expansion by 3.3. L against a constant external pressure of 30.0 kPa c) reversible isothermal expansion by 3.3 L.