exchange - What is the priority of the waiting non-matched bets, when a match becomes available in Betfair?

Say the back price (odds) on a market is $2.5$.

Then the following time sequence happens:

• 
  
  

  Bettor $A$ places a back bet with price $2.6$, for $\$100$ (it will not match)

  
  


• 
  

  Then bettor $B$ places a back bet with price $2.6$ for $\$200$ (it will not match)

  
  


• 
  

  Then bettor $C$ places a lay with price $2.6$ for $\$100$.

  
  

What will be the matches? What is the match priority rule?

• 
  

  Bettor $A$ will have a full match for his $\$100$ back, because he was earlier?

  
  


• 
  

  Or will bettor $A$ have a $\$33.3$ and bettor $B$ will have a $\$66.7$ partial matches because the available offer will be divided proportionally on the current waiting non matched bets?

  
  


• 
  

  Neither of above, random, or this is not documented at all?

  
  

I've tried to find the answer, but did not even find similar questions on the web.