Sigh - if this was an episode of Radio 4's "Just a minute" somebody would buzz me for "repetition".
The short answer is that the factor to be used is a variable - the only way to find out which one to use is to look in the FLYING SCHOOL OPERATIONS MANUAL and it will be specified in there.
Even if the examiner thinks differently - that is the only figure that you can use to factor for simulated public transport operations, in that particular aircraft, from that particular school, at any airfield.
OPERATIONS MANUAL.