I have a feeling this has probably been discussed before, but I couldn't find any recent thread.

Does anyone know the exact probability of NTGs rewarded after a 5-star win (and also 3-4 stars, but most importantly 5)?

I am interested in this because currently I have an artifact in the museum with 6% + 6% base boost on NTG chance, and it would be interesting to know how far it will be worth upgrading those slots (if at all) for a 100% chance.