A series LCR circuit is connected to an ac source of $220 \mathrm{V}, 50 \mathrm{Hz}$. The circuit contain a resistance $\mathrm{R}=100 \mathrm{\Omega }$ and an inductor of inductive reactance  ${\mathrm{X}}_{\mathrm{L}}=79.6 \mathrm{\Omega }$. The capacitance of the capacitor needed to maximize the average rate at which energy is supplied will be _________ $\mathrm{\mu F}$.