A uniform beam of mass [M] kg and length 5.0 m is supported…

A uniform beam of mass kg and length 5.0 m is supported by, but not attached to, two posts as shown in the figure. The posts are separated by a distance of ℓ = 3.0 m. A person of mass kg starts walking along the beam towards the right. How close can this person get to the right end of the beam without it tipping? (What is x as labeled in the figure?)