I trust this is the right place for a couple of questions related to MPM fares...

1) How are MPM surcharges calculated, when inbound and outbound routings are different, and fall in different surcharge bands?

For example, consider a routing:
Outbound: AAA-XXX-BBB, with TPM at 101% of MPM, so in the 5M surcharge band
Inbound: BBB-YYY-AAA, with TPM at 116% of MPM, so in the 20M surcharge band

How is the total fare calculated? Is it:
- The actual mileage averaged on a half-round trip basis? ie: (101%+116%)/2 = 108.5%, so 10M surcharge band?
- The surcharge bands averaged on a half-round trip basis? ie: (5M+20M)/2 = "12.5M", so 15M surcharge band?
- The highest applicable surcharge band applied to the entire ticket? ie: 20M
- Something different?

2) Are surface sectors counted towards TPM, and hence part of the MPM allowance? (I think that it is included in SkyTeam RTW fares, but I don't know about other 'standard' MPM fares?)

Thanks!