A thermodynamic process is shown in figure. The pressures and volumes corresponding to some points in the figure are:

$\begin{array}{l}{\mathrm{P}}_{\mathrm{A}}=3\times {10}^4\mathrm{Pa}\\ {\mathrm{P}}_{\mathrm{B}}=8\times {10}^4\mathrm{Pa}\text{ and }\\ {\mathrm{V}}_{\mathrm{A}}=2\times {10}^{-3}{\mathrm{m}}^3\\ {\mathrm{V}}_D=5\times {10}^{-3}\mathrm{m}\end{array}$

In process AB, 600 J of heat is added to the system and in process BC, 200 J of heat is added to the system. The change in internal energy of the system in process AC would be