Puzzle 81 - Running track.

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The diagram shows a rectangular field with a length of 200m and a width of 50m. Billy runs around the oval track shown, making contact with the fences of the field four times.
Billy says that he has run more than 500m but less than 600m.
Jenny says that he has run more than 400m but less than 500m.
Maggie says that he has run more than 300m but less than 400m.
Who is correct?

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