计算机软件两大类可分为（）

A．操作系统和数据库

B．数据库和应用程序

C．操作系统和语言处理程序

D．系统软件和应用软件

5.Greenfields Co specialises in manufacturing equipment which can help to reduce toxic emissions in the production of chemicals. The company has grown rapidly over the past eight years and this is due partly to the warranties that the company gives to its customers. It guarantees its products for five years and if problems arise in this period it undertakes to fix them, or provide a replacement product.You are the manager responsible for the audit of Greenfields and you are performing the final review stage of the audit and have come across the following two issues.Receivable balance owing from Yellowmix CoGreenfields has a material receivable balance owing from its customer, Yellowmix Co. During the year-end audit, your team reviewed the ageing of this balance and found that no payments had been received from Yellowmix for over six months, and Greenfields would not allow this balance to be circularised. Instead management has assured your team that they will provide a written representation confirming that the balance is recoverable.Warranty provisionThe warranty provision included within the statement of financial position is material. The audit team has performed testing over the calculations and assumptions which are consistent with prior years. The team has requested a written representation from management confirming the basis and amount of the provision are reasonable. Management has yet to confirm acceptance of this representation.Required:

(a) Describe the audit procedures required in respect of accounting estimates. (5 marks)