The highest of: and / or

Question

Do I use and or or with the highest?

Is it:

The highest of a and b.

or

The highest of a or b.

?

Answer 1

Usually, a group of objects follows after 'the highest of':

Mount Harvard is the highest of the Collegiate Peaks of Colorado and the third highest peak of the Rocky Mountains. ¹

Therefore, I'd go for 'and' in your case, but it still sounds unnatural to me.

For numbers or quantities, it is more common to talk about the maximum:

What does this function return? The maximum of A and B.