Ok.

Using a 'standard' 7% discount rate to reflect risk, since this investment is at least twice as risky as a 10-year bond (though some would argue with that point).

Remember, this model looks at production over a mine life of 25 years (anything beyond that doesn't add much at all to NPV). 50k oz/year would only be 1.25M oz over 25y, so I don't much see the point there, but what the hey - it's just an exercise. I can look at it with production ramping up, varying year to year over the course, etc. There are lots of parameters to tweak. These results are with fixed POG, mining costs, production, etc., so not terribly exciting, but I suppose it's a decent starting point.