A series LCR circuit driven by 300 V at a frequency of 50 Hz contains a resistance $\mathrm{R}=3 \mathrm{k} \Omega$, an inductor of inductive reactance $\mathrm{X}_{\mathrm{L}}=250 \pi \Omega$ and an unknown capacitor. The value of capacitance to maximize the average power should be : (Take $\pi^2=10$ )