The intensity of light (in lumens per square meter) at a distance $d$ meters from a point source follows the inverse square law: $I = \frac{P}{4\pi d^2}$, where $P$ is the power in lumens. Two lights are positioned 10 meters apart: Light 1 (100 lumens) at position 0 and Light 2 (400 lumens) at position 10. At what distance from Light 1 is the combined intensity minimized?