Which response code is transmited if a SAG receives two different response codes from each SA?

I have a theoretical doubt about SBC behaviour on the following scenario: a given SBC on a peering environment with two realms and a SAG with two SA in one of the realms. Which sip response would be returned to initiating realm if each SA returns the SBC different response codes assuming they didn't stop recursion? Could it be possible to configurate the behaviour?

 

For example, what if SA1 returns a 408 and SA2 returns a 500? Is there a rule for this behaviour?

 

                              _________
                             |                |                   -> INVITE->
                             |                |---------           Session Agent 1
                             |                |                   <- SIP Code: 408 <-

 -> INVITE->          |                |  
SA originating     ----|     SBC    | 

<- ??? <-                |                |                   -> INVITE->