Your client is a medium-sized company and is a leader in its small industry of producing replica vehicles of classic automobiles. Customers are either very wealthy individuals or from the entertainment industry (for example, movie production studios that require automobiles typical of a certain era). The company uses a proprietary accounting software package that includes a purchases journal, perpetual inventory account, and sub-ledgers for both accounts receivable and accounts payable. Purchases are recognized on receipt of goods, and receiving reports are matched to the purchase order from the unmatched purchase order file. Records and source documents include bank statements, cancelled cheques, purchase orders, sales invoices, shipping records, and time records for employees. There are 27 employees, most of whom are long-term staff. The company is privately owned by three individuals, and the audit is required in order to comply with a covenant in a lending agreement with a large institutional investor (a venture capital fund). Required For each of the following management assertions, design a substantive audit program (one or two procedures, such as reconciling, tracing, and listing). Do not include selecting a sample as one of your procedures. (a) Existence or occurrence of sales (b) Completeness of accounts payable (c) Valuations or measurement of accounts receivable