\(\frac{E}{16 R} R_3=12 R_1\)
\(R_{\text {net }}=4 R_1\)
\(i=\frac{E}{4 R_1}\)
\(P=\frac{E^2 R_1}{16 R_1^2}=\frac{E^2}{16 R_1}\)
\(P_2=\frac{9 E^2}{256 R_1{ }^2} \cdot 4 R_1=\frac{9 P}{4}\)
\(P_3=\frac{E^2}{256 R_1{ }^2} \cdot 12 R_1=\frac{3 E^2}{64 R_1}=\frac{3 P}{4}\)
\(P+\frac{9 P}{4}+\frac{3 P}{4}=\frac{16 P}{4}=4P\)