1. Choose types that preserve meaning
Identifiers remain strings. "2"*3 repeats text as "222"; int("2")*3 gives 6. quantity and price are parsed integers under the source contract; order dates retain an explicit ISO representation.

2. Iterate with a clear population rule
get supplies a starting zero for a new month before adding its line value. The complete result is April 60000 cents, May 59000 and grand 119000. The completed population has 42 lines and 21 distinct orders.

3. Test boundaries and explain the result
Monthly sums reconcile to 119000 cents. AOV is 1190/21≈56.6667 EUR. A valid quantity increase changes value by that line’s unit price without changing key uniqueness. Three cancelled orders remain outside the reported population.
