You are the audit manager on the audit of Blue Stone Ltd (BSL) for the year ending 30 June 2023. As part of the final review stage of the audit, you reviewed the audit working papers and noted the following three matters: * The audit working papers for vouching property, plant and equipment indicate that an invoice for a major asset acquisition during the financial year was not sighted. The junior auditor noted that he is waiting on this documentation from management. All other items selected were vouched to supporting documentation. * The bank confirmation filed in the audit working papers is a photocopy sent to the junior auditor by the financial controller at BSL. The bank sent the original bank confirmation to BSL directly. * Some of the audit working papers were not signed off and dated by the audit staff member at the audit firm who performed the work. Required: 1. ASA 500 requires auditors to design and perform audit procedures to obtain sufficient appropriate audit evidence to be able to draw reasonable conclusions on which to base the auditor's opinion. Explain what is meant by 'sufficient appropriate audit evidence and describe how can auditors obtain sufficient appropriate audit evidence (i.e., what factors could affect the reliability of audit evidence).

2. For each of the three matters noted during the final review stage, explain why they raise a concern about whether sufficient and appropriate evidence has been obtained.