When the current through R 1 is I 1,

The voltage at both ends is U 1=E-I 1? R2

So P 1=I 1? U 1=I 1(ε-I 1？ R2)=-I 12？ R2+EI 1=-R2？ (I 1-E2R2)2+E24R22

When I1= e2r2 = 62×15a = 0.2a.

The power of R 1 is the largest, and p1m = E24R22 = 624×15w = 0.6W.