I don't think infinite is really a fitting value here. At least, it doesn't reflect my belief. I would say each human is invaluable/of indeterminable worth. Again, following that math thing, assuming the worth of each person is x, 5 (or 4, I forget)x > x
Even so, I wouldn't say this is how I think of it. From my religious viewpoints (Assuming that I cannot discern any physical, mental, or religious characteristics) , I would be more inclined to save the five, giving more opportunities for religious safety than just one.
Also, let's not forget that each person influences every person they come into contact with. I would guess they would have some sort of "good" story to tell about this, possibly influencing others they come into contact with. Also, I would prefer to save more than one family the trauma of a death.
Also, in some situations it seems that not attempting to prevent the deaths of more is about the same as killing them. By not doing something to prevent it, you might as well be saying that the action is acceptable, and you support it.
As much as this makes sense to me, it still sounds sick and wrong, using logic to weigh the lives of actual human beings. ._.
Laka