{"blocks": [{"key": "95d1607f", "text": "Scenario", "type": "header-two", "depth": 0, "inlineStyleRanges": [], "entityRanges": [], "data": {}}, {"key": "7ca9a172", "text": "Video-recommendation system selecting videos from a large inventory to show individual users and their friends.", "type": "unstyled", "depth": 0, "inlineStyleRanges": [], "entityRanges": [], "data": {}}, {"key": "36113273", "text": "Question", "type": "header-two", "depth": 0, "inlineStyleRanges": [], "entityRanges": [], "data": {}}, {"key": "d4387cc2", "text": "If K videos are randomly chosen from N distinct videos, what is the probability a particular video appears in the set? Two friends each receive K videos without replacement from the same inventory. What is the probability they share at least one identical video? Should we push identical videos to friends or diversify their feeds? Discuss expected engagement impact and trade-offs.", "type": "unstyled", "depth": 0, "inlineStyleRanges": [], "entityRanges": [], "data": {}}, {"key": "8a296181", "text": "Hints", "type": "header-two", "depth": 0, "inlineStyleRanges": [], "entityRanges": [], "data": {}}, {"key": "07072f75", "text": "Apply combinations and complementary probabilities; link calculation to user engagement reasoning.", "type": "unstyled", "depth": 0, "inlineStyleRanges": [], "entityRanges": [], "data": {}}], "entityMap": {}}