In a cyclic process, work done is equal to the area under the cycle and is positive if the cycle is clockwise and negative if the cycle is anticlockwise.
$\therefore$ The network done by the gas is
$W =$ Area of the cycle $ABCA$
$=\frac{1}{2} \times(7-2) \times 10^{-3} \times(6-2) \times 10^{5}$
$=\frac{1}{2} \times(5) \times 10^{-3} \times 4 \times 10^{5}$
$=10 \times 10^{2} J=1000\, J$
