Crit Debuff question

[Ferth]

I was talking to a friend and we didn't have an answer for this from the top of our heads:

Let's assume I have 20% crit chance after all personal stats are accounted for.

An enemy is debuffed by an action that claims to boost crit rate on that target by 20%

Is my resulting chance to crit on that target 40% or 24%?

Also, does the increase of critical rate on that target only affect the rate, or can it also boost my critical damage?

I apologize if this has been asked before, my search-fu failed me.

We really won't know how SE decides to do the math on this until we can test it... or they straight up tell us, which is unlikely.