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An unknown green charge (with a #1 on it) is shot into a region containing four fixed charges (numbered 2--5), one of which is known to be positive (the red one). You can measure position using a mouse down (position is given in meters and time is given in seconds). Restart.

Determine the signs of the unknown charges. You may consider neutral as a possible answer. Justify your response.

Problem authored by Scott Bonham and modified by Melissa Dancy.