Let f(x)=x2−12x. To prove that limx→6f(x)=−36, we proceed as follows. Given any ϵ>0, we need to find a number δ>0 such that if 0<|x−6|<δ, then |(x2−12x)−(−36)|<ϵ. What is the (largest) choice of δ that is certain to work? (Your answer will involve ϵ. When entering your answer, type e in place of ϵ.)