A series AC circuit containing an inductor (20mH), a capacitor (120...

(Power factor), ${P}_{f} = cos \text{ϕ} = \dfrac{R}{Z}$

Where $R, Z$ are the resistance and impedance respectively.
(Energy dissipated) $E = {V}_{rms}^{2}Z \times cos\text{ϕ} \times t$
$⇒ E = {V}_{rms}^{2}Z \times \dfrac{R}{Z} \times t$

$⇒ E = {V}_{rms}^{2}{Z}^{2} \times R \times t$

${V}_{rms}, t$ are the RMS voltage and time respectively.

We know that the Impedance of a LCR circuit is given by the formula,
${Z}^{2} = {R}^{2} + {\left(\text{\omega}L - \dfrac{1}{\text{\omega}C}\right)}^{2} ⇒ {Z}^{2} = {60}^{2} + {\left(2\text{\pi} \times 50 \times 20 \times {10}^{- 3} - \left(\dfrac{1}{2\text{\pi} \times 50 \times 120 \times {10}^{- 6}}\right)\right)}^{2}$

Where $\text{\omega}, L, C$ are the angular frequency, inductance and capacitance in the circuit respectively.
$⇒ {Z}^{2} = {60}^{2} + {\left(2\text{\pi} - \dfrac{1000}{12\text{\pi}}\right)}^{2}$

$⇒ {Z}^{2} = 4009 . 7$

$∴ E = \dfrac{{24}^{2}}{4009 . 7} \times 60 \times 60J$

$= 517 . 14J$

$= 5.17 \times {10}^{2}J$