Two identical plates P and Q, radiating as perfect black bodies, are kept in vacuum at constant absolute temperatures $$T_P$$ and $$T_Q$$, respectively, with $$T_Q < T_P$$, as shown in Fig. 1. The radiated power transferred per unit area from P to Q is $$W_0$$. Subsequently, two more plates, identical to P and Q, are introduced between P and Q, as shown in Fig. 2. Assume that heat transfer takes place only between adjacent plates. If the power transferred per unit area in the direction from P to Q (Fig. 2) in the steady state is $$W_S$$, then the ratio $$\frac{W_0}{W_S}$$ is ________.