Killer Sudoku Puzzle no 6

Usual sudoku rules apply i.e. each row, column and 3x3 mini-grid must have all of the numbers 1 to 9 exactly once. The puzzle is also divided into smaller areas called cages, which are surrounded by dashed lines. Numbers are not repeated within a cage. The number in the top left hand corner of each cage shows the sum of the numbers in that cage:

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