1) Upon which 2) Whereupon 3) Word of legalese 1) Whereupon 
• (adv.) At what; -- used interrogatively; as, whereat are you offended? • (adv.) At which; upon which; whereupon; -- used relatively.
Where·at' adverb 1. At which; upon which; whereupon; -- used relatively. « They vote; whereat his speech he thus renews.» Milton. « Whereat he was no less angry and ashamed than desirous to obey Zelmane.» Sir P. Sidney. 2. At...
[adv] - in consequence of which 2. [adv] - at or toward which