please answer these 3 questions

1. In Chapter 4, you were asked to identify customers with large total sales volume. One large customer was identified as having an unusually large balance. What substantive procedures should have been completed during the audit to provide evidence that the revenue related to this one customer was fairly stated? 2. In Chapter 5, you forecasted Q4 sales and then compared them to actual sales. This suggested that some months had higher sales than expected. What substantive procedures should have been completed during the audit to provide evidence that revenue during Q4 was not overstated? 3. Final/review analytics provide the auditor with a chance to take one last, big-picture view of the audited entity's financial statements. What purpose does this serve, and how can it be different than detailed substantive testing