The potential difference across a Coolidge tube is $20 \mathrm{kV}$ and $10 \mathrm{mA}$ current flows through the voltage supply. Only $\text{0.5\%}$ of the energy, carried by electrons striking the target, is converted into $\mathrm{X}$-ray. Then the power carried by $\mathrm{X}$-ray beam (in $\mathrm{W}$) is