How would you implement a rules engine to enforce the corporate credit card expense policies, specifically to ensure that no expenses at a restaurant exceed $75 and total meal expenses cannot exceed $200 per trip? Please describe your approach in detail.

``` I would design a microservice that handles expense submissions and validate them against predefined rules. The service would utilize a database to store expense records and rules. Upon a submission, the service would check the expense against various rules using a series of conditional statements or a policy engine to determine if the expense is valid. If the expense meets all criteria, it would be saved; otherwise, an error response would be returned with details on what was violated. ```