The audit manager is reviewing the audit plan prepared by the team leader for the audit of the trade payables balance. In an attempt to be more efficient, the team leader has suggested that more than one assertion can be covered by the same audit procedure, as shown below: Obtain a breakdown of the items from the trade payables balance. Take a sample of items from this and agree them to supporting documentation such as an invoice (existence; rights & obligations; accuracy, valuation & allocation; completeness) For each of the assertions listed above explain whether the proposed substantive procedure is appropriate. If it is not, then suggest an alternative substantive procedure that would be appropriate for that assertion.