I didn’t use Rita’s book personally but many PMP aspirants recommend it. I suggest using Rita’s book as a study guide and focus more on PMBOK since the exam focus is on PMBOK. PMBOK can be vague and so Rita’s book comes in handy helping you understand better some of the processes and knowledge area.
Reserves can be determined by adding up all the cost and schedule reserves in all these planning processes.
When Performing Quantitative Risk Analysis, you are analyzing the effect of each identified risk on your overall project performance. For example, if one of the identified risk is that one of your key engineer resign in the middle of the project, your risk response is you need x number of days to hire one with a budget of $x. The number of days and cost will then be added to your schedule and cost baseline.
Would you determine cost and schedule reserves in the Estimate costs, Determine Budget, and Estimate Activity Durations process or during the Perform Quantitative Risk Analysis process (as Rita's book is claiming?