I want to make a system that tests for a specific player at specific coordinates with a specific item? And also how do I get one redstone output out of all the commands at once?  

I tried to do /testfor [x=X,y=Y,z=Z,r=R]  

And /testfor {Inventory:[{id:"minecraft:slime\_ball"}]}  

Both work, but I can't test for 1 specific player, I can **only** check for **all** the players, I need help please.