1. How would you create APIs for a Calendly-like application?
2. Recycling Pens Problem Statement Imagine you have a certain number of empty pens, and some money in your pocket. For each pen, you can choose to either recycle it for a reward or buy a refill to make it usable again. Your goal is to find the maximum number of usable pens you can achieve given the constraints. Example: Input: N = 5, R = 10, K = 2, C = 3 Output: 4 Explanation: Recycle one pen to get 2 rupees, resulting in 12 rupees. With this, buy 4 refills and combine with 4 pens to make them usable, achieving the maximum of 4 usable pens. Constraints: 1 ≤ T ≤ 10^5 1 ≤ N ≤ 10^9 0 ≤ R ≤ 10^9 1 ≤ K ≤ 10^9 1 ≤ C ≤ 10^9 Time limit: 1 sec Input: The first line contains integer 'T', the number of test cases. Each test case consists of four space-separated integers: 'N', 'R', 'K', and 'C'. Output: For each test case, output the maximum number of usable pens. Note: No need to print anything. Just implement the solution function and return the result.
3. Create a Key Performance Indicator (KPI) to track customer satisfaction.
4. Typical AWS and Kubernetes Concepts
5. Design a two-factor authentication system.