Its been a little while since I did this exam, and I recall the question, probably because it was also in all the practice exams I did.
To answer outnabout. When I did the CPL 7 exam series, you often stumbled across PPL aimed questions. My take on it, was that they were designed to test your knowledge of the regulations.
As for Fuel flow, they give a figure if they want the answer in litres or gallons (and yes they do that to you...mix up the units in use)
Unless I have missed a rule change (and that is quite possible), the rule for Private ops, is 'Sufficient fuel for the planned flight' In the Exam, the CAAP is a trap for you to get the question wrong.
For the purpose of this question, 45 minutes reserve is not the figure you use. IIRC, using 10 minutes got you close enough to make the correct choice on the exam.....
Reading the CAAP, civil aviation ADVISORY publication, it doesn't take too many IQ points to realise that the whole document is suggestive. Simply reading the section headers is enough....the use of the word should in place of shall.
After that it comes down to quality of lawyer to argue prosecution and defence.
enjoy.