how do I solve this?

5. L-dopa is used in the treatment of Parkinson's disease. Identify the four most acidic protons and arrange them in order of increasing acidity. 6. Coumarins are a class of natural products produced by plants and animals. It has a wide variety of applications in cosmetics, food industry and fluorescent laser dyes. In the 1 HNMR spectrum of coumarin derivate shown below, the two signals farthest downfield are at 7.38 and 8.42pm. Identify the two protons that most likely give rise to these signals and justify your answer using resonance structures