A classic histogram records request durations. Which expression estimates the fleet-wide 95th percentile while preserving bucket boundaries?

1. histogram_quantile(0.95, sum by (le) (rate(request_duration_seconds_bucket[5m])))
2. histogram_quantile(95, sum(rate(request_duration_seconds_bucket[5m])))
3. avg(request_duration_seconds_bucket)
4. sum(histogram_quantile(0.95, rate(request_duration_seconds_bucket[5m])))