Suppose I am using a +3 Staggering flail to Eldritch Strike, and I have the Flail Expertise feat. I hit (but not critically) and knock my target prone using Flail Expertise. What is the maximum number of squares I may slide the target, using just the three linked things (one feat, one item, one power), but not Staggering flail's daily power: 0 or 3?

Suppose further that I have the Lashing Flail feat. Same question, but with the four linked things instead of three: 0, 1, 3, or 4?

Thanks.