Combining tables analytical accounting

Merge the 2nd and 3rd table into the first one, expanding the cost and percentage columns from each, and then define a new custom column that multiplies the percentages with the initial amount.

let
    Source = Centers,
    #"Grouped Rows" = Table.Group(Source, {"Booking reference"}, {{"Amount", each List.Sum([Amount]), type nullable number}}),
    #"Merged Queries" = Table.NestedJoin(#"Grouped Rows", {"Booking reference"}, Centers, {"Booking reference"}, "Centers", JoinKind.LeftOuter),
    #"Expanded Centers" = Table.ExpandTableColumn(#"Merged Queries", "Centers", {"Cost center", "Percentage"}, {"Cost center", "Center%"}),
    #"Merged Queries1" = Table.NestedJoin(#"Expanded Centers", {"Booking reference"}, Places, {"Booking reference"}, "Places", JoinKind.LeftOuter),
    #"Expanded Places" = Table.ExpandTableColumn(#"Merged Queries1", "Places", {"Cost place", "Percentage"}, {"Cost place", "Place%"}),
    #"Added Custom" = Table.AddColumn(#"Expanded Places", "Custom", each [#"Center%"] * [#"Place%"] * [Amount], type number)
in
    #"Added Custom"

See the attached file.