I don't know the "right" answer to your question, but I can tell you that you need at least 180W of light above each mirror for enough illumination to apply makeup - and even that is a little low. My pet peeve is not enough light in a bathroom, hotels are notorious for this. I don't think one light on either side of a mirror is adequate, unless each bulb is 100W and you have 4 of them over a vanity (two mirrors, 4 lights).
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Accessible white
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