\(30p=0,5h\)
a. \(\left\{{}\begin{matrix}A1=P1.t=40.0,5=20\left(Wh\right)=72000\left(J\right)\\A2=P2.t=60.0,5=30\left(Wh\right)=108000\left(J\right)\end{matrix}\right.\)
b. \(\left\{{}\begin{matrix}R1=\dfrac{U1^2}{P1}=\dfrac{200^2}{40}=1000\Omega\\R2=\dfrac{U2^2}{P2}=\dfrac{200^2}{60}=\dfrac{2000}{3}\Omega\end{matrix}\right.\)
c. \(R=R1+R2=1000+\dfrac{2000}{3}=\dfrac{5000}{3}\Omega\)