Checkpoint
One last thing before we move on. Same surface as a write step — but the lesson doesn't complete until this passes.
Run the monthly cost review as code. Print the total, then every line item sorted by cost descending as f"${cost:>5} {util:>4.0%} utilized {name}" — appending " <- LEAK" when utilization is under 20%. Close with the halving lever for the biggest line item: f"halving lever for '{name}': {lever}" from the LEVERS dict. Biggest item, utilization, one change that halves it — the three questions, mechanized.