This is unclear. Do you mean that rationality can be a quantity which, if >1 means one thing, and if <1 another? I’d have written it something like
utility(x)>cost(x) ⇒ rationality(x) = TRUE

I prefer a scale of 0 to 1, ranging from zero utility to maximum utility.

So, there’s no need for a Truth value there, merely a simple division.

I’ll admit that there might be an alternative scale possible that includes ‘-1’ for maximum negative utility but that would require me to think about it … which it’s far too late for me to attempt at this time of the morning, I’m afraid — I’ll have to get back to you on that one.

This seems to me to be a reformulation of 2.

It’s the formulation of of the equation for calculating the rationality of a decision/action — step 2 is simply the working that clarifies it.