I have found students generally enjoy this activity and find it more concrete than the work that they have just done on rate of change equations. They struggled with Q3 in general and part (d) in particular. I think because the find it hard to believe that any exponential function will dominate any power function. It is also difficult because they are asked to generalize by themselves which is always a difficult step. It is good to talk to small groups during this process and to have a whole class discussion when everyone has worked on it. If this is where you break to send them away (which is appropriate so that students have time to think about this question) it is a good idea to ask students to formulate a plan for part (d) before leaving the classroom. Students struggle again with Q7 where they are being asked to reason algebraically from a set of statements that we are taking to be true about how sums of functions behave and which types of functions dominate in the long term. I think it can be helpful to discuss this question in class and ask a number of students to explain their reasoning process.