Invoice a plumbing firm's jobs with a call-out hour, labour in started quarter hours, emergency rates and banded parts markup

# Invoice a plumbing firm's jobs with a call-out hour, labour in started quarter hours, emergency rates and banded parts markup Inputs: `jobs.csv` (job_id, customer_id, arrive, depart, emergency), `parts.csv` (line_id, job_id, part, qty, unit_cost), `customers.csv` (customer_id, name, service_plan) and `rates.json` (callout_fee, labour_per_hour, emergency_multiplier, markup_bands, tax_pct). All customers and jobs are synthetic; amounts are in dollars and times are local. These rules are the firm's policy; where `office-note.txt` disagrees, the rules win. Rules: - Labour: the first 60 minutes on site (depart − arrive) are covered by callout_fee, charged even for a shorter visit; time beyond 60 minutes is billed in started 15-minute blocks at labour_per_hour ÷ 4 per block; customers whose service_plan is 'yes' pay no callout_fee (their blocks are still charged); an emergency job ('yes') has its whole labour charge multiplied by emergency_multiplier, rounded half-up to the cent. - Parts: each part line is marked up by the first band in markup_bands whose max_unit_cost is at least the line's unit_cost (null = no limit); line price = qty × unit_cost × (100 + pct) / 100, rounded half-up to the cent. - Tax: tax_pct of the job's parts total, rounded half-up to the cent per job; labour is not taxed. Job total = labour + parts + tax. - Write `out/invoices.json`: `{"parts": {"<line_id>": <dollars>, ...}, "jobs": {"<job_id>": {"labour": <dollars>, "parts": <dollars>, "tax": <dollars>, "total": <dollars>}, ...}, "customers": {"<customer_id>": <sum of the customer's job totals>, ...}}`. `parts` has one entry per row of parts.csv and `jobs` one entry per row of jobs.csv (a job with no parts has parts 0 and tax 0). - Roll-ups: Customers in customers.csv with no jobs are left out. ## How this run works - Work on your own: nobody will answer questions in this task, and writing to `ask/` counts against the run. - Write only under `out/`. Create `out/` if it is missing. Inputs are synthetic; don't fetch anything from the network. - Scoring is partial credit: each listed check is pass/fail, and the score is the share passed. Numbers are compared to within 0.005 unless the task says otherwise.