How do I calculate the odds of this? (Statistics and probability question)

I’m currently studying with a friend of mine and we came across an exercise we can’t manage to solve:
We have 3 factors:

E = An extremely unlikely event P(E)=0,001=0,1%

Two witnesses A and B, each tell the truth 90% of the time, independently of each other.

They both say the event has happened, what are the odds of this being true?

Our train of thought is that we should first evaluate the odds of both of them telling the truth (being two independent events, the odds are 81%) and then we’re stuck on how to actually calculate the odds of it having happened if they say so.

Has anyone any idea of what we’re supposed to do next?