ALEX
You are correct in concluding that the k factor used in the CRP5 is not 1. I worked it out once (a few months ago) and it turned out to be about 0.86.
The answer 0.8 can also be found by using the table at Figure 4.3 in the CAP 698.
I also agree (as I stated previously) that questions requiring the use of the equation have not been in previous exams. But we must be cautious here. The examiners are constantly devising new questions. Relying entirely on feedback inevitably leads to disappointment when new questions suddenly appear. The cry "That exam was right off the wall, there were no feedback questions" is heard all to frequently after exams.