Build A Quick Tool To Split A Bill Fairly

Someone always ends up doing the maths on a napkin while the table waits, and someone else always insists they only had one drink. This writes a formula or short script that takes items, prices, and who ordered what, then works out exactly who owes what, tax and service charge included, with a worked example to check it first.

Write a small script or spreadsheet formula in {TOOL_TYPE} that splits a shared bill of [total amount] between {NUMBER_OF_PEOPLE} people, where some items are shared equally and others belong to one person only. Take a simple list of items with prices and who they belong to (or 'all' for shared), and output what each person owes, including their fair share of tax or service charge. Show the formula or code, then a worked example with made-up numbers so I can check it works before using it for real.