Assume that you are a newly appointed junior auditor in Grant Thornton, an auditing firm. After a 3- month rigorous training on the job, you have been awarded the certificate of completion and is now ready to embark on your very first assignment. Today, your first job was to evaluate the audit evidence gathered by your team from Nizwa Trading and see if they are reliable or not based on ISA 500. The following are the evidences gathered in various forms: a) Included on file is the letter of confirmation of cash balance received from the companys bank, Bank Nizwa. The letter has the proper letter head, addressed to your audit firm and originally signed by the bank manager. b) Your team has established that internal control of Nizwa Trading is very effective. System is computerized, not manually done, and all controls are in place. When you ask for copy of the sales invoice, the staff in-charge gave them to you immediately on the same day in electronic form. c) Original copy of the building insurance have been provided. However, when you make further inquiries, the insurance company is unknown (never heard of before) or not even included in the list of insurance companies in Oman. You highly doubt the authenticity of the insurance company. d) Upon confirmation of the companys receivable account, management readily gave their oral confirmation that the accounts receivable are fairly presented. e) Also included in the file of audit evidences are photocopies of employment contracts obtained from the Human Resource Department. Required: Evaluate the reliability of each of the documents above and identify the one that is considered the most reliable and least reliable.