Heavy Frost/Hypothermia Interaction (Question)

The Heavy Frost passive tree node ignores non-negative elemental resistances of frozen enemies, and Hypothermia reduces cold resistance... but I'm unsure how they interact if used at the same time.

If, say, a monster has 50% cold resistance and Hypothermia is reducing cold resistance by 35%, does Hypothermia reduce the cold resistance to 15% and then Heavy Frost ignores the 15%, or does Heavy Frost ignore all of the cold resistance and then Hypothermia gives the monster -35% cold resistance?

Obviously, if it's the first case, then Hypothermia isn't doing anything if the monster is frozen. If it's the second, then it's nice boost to cold damage.

I realize that Hypothermia will still be helping with non-frozen enemies, but I'm wondering specifically about freezing a boss, and wondering if Hypothermia is allowing for extra damage, or if it's not doing anything beyond what Heavy Frost is doing.

Thanks for the answer.