Horizontal force on a post in a Hammock

[sun.there]

Your friend of mass m sits in a hammock that is suspended between two vertical posts separated by a distance d. If the hammock dips a distance h below the height l at which the hammock is secured to the posts, what is the horizontal force on each post due to your friend? Use g for the gravitational constant.

 

[CWatters]

https://www.physicsforums.com/showthread.php?t=686781