events +---------+------------+---------+---------------------+ | user_id | event_type | revenue | timestamp | +---------+------------+---------+---------------------+ | 101 | view | 0.00 | 2023-01-01 10:00:00 | | 101 | purchase | 29.99 | 2023-01-01 10:05:12 | | 202 | view | 0.00 | 2023-01-01 11:20:33 | | 202 | purchase | 15.50 | 2023-01-01 11:22:10 | | 202 | logout | 0.00 | 2023-01-01 11:30:45 | +---------+------------+---------+---------------------+ ##### Scenario An e-commerce company stores clickstream events in a Python list of JSON objects; analysts need per-user revenue and average session duration for reporting. ##### Question Write a Python function that takes a list of dictionaries each with keys ['user_id', 'event_type', 'revenue', 'timestamp'] and returns, for every user, total_revenue and average_session_duration (in seconds). Explain complexity. ##### Hints Use one pass with defaultdict. A session starts with the first event and ends with the last for that user; avoid multiple sorts.