How long will it take to fix crossbite/midline shift and close extraction gap? Will elastics alone suffice? (photos)

Midline shift and resulting crossbite due to extractions as a child and retained baby tooth. baby tooth extracted for braces and the plan is to have bottom teeth shift to fill in that space and fix midline. Also slight underbite since top teeth are directly over bottom front. Power chains were placed on bottom shortly after these pictures.

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