If anyone is looking for an interesting question, I have found a good one on a older STEP paper.
*hint*
If you are stuck on part (ii) remembering the property that ln(x) + ln(y) = ln(xy) is useful when trying to find a suitable function.
The question doesnt require any A2 maths knowledge which makes it more accessible.
http://www.admissionstestingservice.org/Images/7922-step-specification.zip