Use the shipping-rate-calculator Skill.

Our packing team needs to understand why large lightweight parcels cost more and our checkout team needs clear shipping rules. Calculate dimensional and billable weight for 20×16×12 inches at 5 lb, 6×6×6 inches at 160 oz, and 50×40×30 cm at 2000 g. Use our planning factors of 139 in³/lb and 5000 cm³/kg and round billable pounds up. Apply the supplied US and Canada store tariffs to the three basket examples, and produce a calculator plus a table the team can check. These are our planning assumptions, not live carrier quotes.

The attached business materials are:
- inputs/baskets.csv
- inputs/merchant.json
- inputs/parcels.csv

Deliver a complete result.md report that the operations team can read, plus any finished files needed for this task. Keep supporting calculations and evidence with the deliverables. Write the report in English; use the requested target language for customer-facing copy. The business datasets are fictional examples unless the brief explicitly names a live public website.