A system consists of a light horizontal rod of length L supported by two light vertical rods of length l each as shown below. Points A, B, C, D are frictionless pivots. A small sphere of mass M is attached to the horizontal rod at a distance d from the midpoint of the rod. What is the period of small-amplitude oscillations of this system in the plane of the page?

(Submitted by Don Easton, Lacombe, Alberta, Canada)

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