How much pure gold are there in the specimen?

I have this really hard question for minerology. Here is the question: A specimen of rich gold ore weights 309.3g and its volume is 82,9 cc; quartz (G=2.65) is the only gangue mineral. The alloy contains 12.1% silver, the density of the alloy being 17.5 g/cc. How much pure gold are there in the specimen?