Trim Problem

Hello every one!

i have a query in reference to this post, http://www.grasshopper3d.com/forum/topics/help-7?commentId=2985220%... 

i was trying to make these chairs given in attached image on this post while i encountered a problem. i am unable to trim the lines i have mentioned in the attached image for some reason. i have also added the .gh file for reference.

any help would be appreciated.

thanks!