Sequence(Date(thisRow.year,01,01),Date(thisRow.year,12,31)).Filter(CurrentValue.WeekNumber() = thisRow.[my weeknumber]).FormulaMap(CurrentValue.monthname()).WithName(TheMonths,
Sequence(1,TheMonths.Count()).FormulaMap(TheMonths.Nth(CurrentValue) =TheMonths.First()).CountIf(CurrentValue=True()).WithName(OutCome,
If(OutCome >=4, TheMonths.First(), TheMonths.Last())
)
)