2008 Q 4c

[apparition]

This question is driving me crazy. Did anyone do it? do u find it easy?

in particular, i don't get why:

1. avg size = 100 in the solution, when the question clearly states it is 100,000

2. "Reserve Credit" does not get multiplied by "conversions/radix", when everything else (i.e. "option expense" and "option charge") do get multiplied by "conversions/radix"

3. my head would only spin clockwise, and never anticlockwise

Thanks.