What is the order of damage reduction?

I'm trying to calculate the effect of an additional 25% armor and 2% damage reduction. It should all be multiplicative so it shouldn't matter the order?

I am receiving a 20k phys hit as a blood spec DK and I want to see what the difference would be if I was Frost with UA activated. Can I simply reduce that by another 2% (Imp Frost Pres) and then the additional armor reduction (not sure what 8k armor reduction is)? Or will I need to reverse the order to find out the unmitigated damage and then re-calculate the damage reduction?

1) For reference, what is the order of incoming damage?

2) How much reduction does each point of armor provide? I can calculate 8k armor from there.

Thanks