A sample of a monatomic ideal gas undergoes the three-step cyclic process \(1 \rightarrow 2 \rightarrow 3 \rightarrow 1\) shown in the \(PV\) diagram. Process \(1 \rightarrow 2\) is an isobaric expansion at a pressure of \(2.0 \times 10^5 \text{ Pa}\) from an initial volume of \(1.0 \times 10^{-3} \text{ m}^3\) to a final volume of \(4.0 \times 10^{-3} \text{ m}^3\). Process \(2 \rightarrow 3\) is an isochoric pressure decrease, and process \(3 \rightarrow 1\) is an adiabatic compression during which \(300 \text{ J}\) of work is done on the gas. What is the thermal efficiency of this cycle?