I'll be flying PHL-TPE later this year on a US codeshare with UA in business class, and will be Silver Preferred by that point. Here's the question...there are bonus miles awarded for being Silver and also for flying business class, but how does US award them? Are business class bonus miles added to the base mileage before the Silver bonus is awarded (meaning a double bonus) or are both sets of bonus miles added to the base mileage for the flight?

Example:
10K base mileage (for estimating purposes only). If the 5,000 mile (50%) Business Class bonus is added first, then is the Silver bonus 25% of 15,000 or 25% of the base 10K?

I know it's nit-picking, but there's a chance I could make Gold by the end of the year depending on how bonus miles are awarded.

Thanks!