I have a question regarding how RDM/Elite Bonuses are calculated. Assume, for the moment, that I have booked a fare (A/C/D/J/Z) that earns a 150% RDM bonus (calculated based on BIS base earning), and that would also earn a 225% Plat Bonus (which I believe is calculated against BIS, rather than an RDM-bonus-adjusted amount). For the purpose of simplicity, assume the BIS earnings for this fare is 100mi (ignoring the 500mi minimum earnings). Some logical/mathematical steps have been abbreviated/omitted.

Here is how I would calculate the total bonus earnings:

100 BIS x 225% (Plat Bonus) = 225mi.
Additional RDM Bonus Calculation: 50% of 100 BIS = 50mi.

The sum of 225 and 50 is 275, yielding the actual earned RDM amount for this theoretical flight. (i.e., the Plat Bonus is calculated as against BIS earnings of 100mi rather than the RDM-bonus-adjusted figure of 150mi.).

Is this correct, or does the bonus earning calculation look like:

RDM Bonus applied to BIS of 100mi: 100 x 150% = 150mi.
Plat Bonus applied to adjusted amount: 150 x 225% = 337.5mi

Which of the two is correct? If neither, what is the correct calculation method?