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.

## Approach 1. Set up a microservice architecture to handle expenses submission. 2. Utilize a relational database (e.g., PostgreSQL) to store expenses and rules. 3. Implement validation logic for each rule as per requirements (e.g., using if-else conditions or a rules engine). 4. Return appropriate messages for valid and invalid expense submissions. ## Complexity **Time:** O(n), where n is the number of rules checked. **Space:** O(m), where m is the number of expenses stored in the database. ## Trade-offs - Straightforward implementation vs. using a more complex rules management system.