A $3$-phase, star-connected, balanced load is supplied from a $3$-phase, $400 \mathrm{~V (rms),}$ balanced voltage source with phase sequence $\text{R-Y-B},$ as shown in the figure. If the wattmeter reading is $-400 \mathrm{~W}$ and the line current is $I_R=2 \mathrm{~A}(\mathrm{rms})$, then the power factor of the load per phase is
- Unity
- $0.5$ leading
- $0.866$ leading
- $0.707$ lagging