For what X is this easiest : Run X hour marathon and Bench X hundred pounds

Need to be able to do both efforts on the same day

Some points along this curve...
X=2 - 2:00 marathon and 200 lb bench
X=2.25 - 2:15 marathon and 225 lb bench

X=2.5 - 2:30 marathon and 250 lb bench

X=3 - 3:00 marathon and 300 lb bench

X=6 - 6:00 marathon (~13:45 place) and 600 lb bench
X=7 - 7:00 marathon (~16:00 pace) and 700 lb bench

The easiest is somewhere in the middle. What's the smallest and largest X for which someone could/has done this?