Space War Puzzle

The Space War Puzzle provides some insight into the perplexities of simultaneity and relative positions at high-speed flight. You were standing on the Moon, watching two fast spaceships passing directly overhead, flying line astern at constant speed and distance apart. Exactly when the two ships were equidistant from you (as you saw them - refer to sketch), you observed each to fire a single missile simultaneously and directly towards each other. The two missiles however collided and exploded spectacularly, but harmlessly.

If the speeds of the missiles relative to their respective ships were identical, where, in the inertial frame of the two ships, did that collision happen: (i) equidistant from the two launchers; (ii) closer to the front launcher; (iii) closer to the rear launcher?