Verified answer

I am doing the OCR version (as). I think it will be something like pollution permits or of that kind. I hope you remember how to answer it:

1. Definitions and problems - linking problems to market failure

2. Draw a graph of the solution (solution is easier and less likely to go wrong)

3. Explain graph - advantages of solution and disadvantages of solution

4. Compare to other solutions - advantages and disadvantages of alternative

5. Conclusion - which is better solution

If this is your essay structure I hope I helped!