a) Explain with examples how validity checks, completeness tests and reasonableness tests can be implemented in a computerised accounting system to ensure accuracy of customer orders in the revenue cycle.

b) Explain how a post-billing system and a pre-billing system is used in the revenue cycle. Discuss with an example what types of businesses would use a post-billing system and a pre-billing system and justify why the business has selected that billing system instead of the other.