The capacitive reactance of the circuit is given by, 

$\begin{array}{rcl}{\mathrm{X}}_{\mathrm{c}}& =& \frac{1}{\omega \mathrm{C}}\\ & =& \frac{\pi }{2\pi \times 50\times {10}^{-3}}\\ & =& 10 \mathrm{\Omega }\end{array}$

The inductive reactance of the circuit is given by, 

$\begin{array}{rcl}{X}_L& =& \omega L\\ & =& 2\pi \times 50\times \frac{100}{\pi }\times {10}^{-3}\\ & =& 10 \mathrm{\Omega }\end{array}$

From above calculations, it is clear that

$X_C=X_L$

$\therefore$ Power factor $=\frac{R}{Z}=\frac{R}{R}=1$