(a)
\(P_2=P_1 -\frac{2 T}{R}=P_0- \frac{2 T}{R}\)
\(P_3=P_2+\rho gL=P_0- \frac{2 T}{R}+\rho gL\)
here \(r=R \cos \theta=R\)
\(P_4=P_3-\frac{2 T}{R}=P_0- \frac{4T}{R}+\rho gL\)
\(P_4=P_0\)
\(\Rightarrow L p g=\frac{4 T}{R}\)
\(\Rightarrow L=\frac{4 T}{R p g}\)