The process 1-2 is isobaric therefore work done by the gas is

${\mathrm{W}}_{1\to 2}=\mathrm{n}\mathrm{R}\mathrm{\Delta }\mathrm{T}=2\times \mathrm{R}\times 300$

${\mathrm{W}}_{1\to 2}=600\mathrm{R}=4980\mathrm{ }\mathrm{J}$

The process 3-1 is isochoric therefore work done by the gas is zero.

Therefore,

${\mathrm{W}}_{1\to 2\to 3\to 1}={\mathrm{W}}_{1\to 2}+{\mathrm{W}}_{2\to 3}$

Also for cyclic process,

$\mathrm{\Delta }\mathrm{W}=\mathrm{\Delta }\mathrm{Q}$

${\mathrm{W}}_{1\to 2}+{\mathrm{W}}_{2\to 3}+0=\mathrm{\Delta }\mathrm{Q}$

$4980\mathrm{J}+{\mathrm{W}}_{2\to 3}=-300\mathrm{J}$

${\mathrm{W}}_{2\to 3}=-5280\mathrm{J}$