An inductor of inductance $L,$ a capacitor of capacitance $C$ and a resistor of resistance $R$ are connected in series to an ac source of potential difference $V$ volts as shown in figure.$\newline$Potential difference across $L, C$ and $R$ is $40 V, 10 V$ and $40 V,$ respectively. The amplitude of current flowing through the LCR series circuit is $10 \sqrt{2} A.$ The impedance of the circuit is: