A fixed mass of gas has an initial volume of 
at a pressure of 
and a temperature of 
. It is heated at constant pressure so that, in its final state, the volume is 
at a temperature of 
, as illustrated in the figure below.
The total thermal energy supplied to the gas for this change is 
. Determine
the external work done,
the change in internal energy of the gas. State whether the change is an increase or a decrease in internal energy.
