Stacked cubes

What is the total surface area of this shape?
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Problem



Image
Stacked cubes


Three cubes have been glued together as shown in the diagram.

The side length of the smallest cube is 3 cm.

The side length of the medium cube is 5 cm.

The side length of the largest cube is 8 cm.

What is the total surface area of the figure?

This problem is taken from the World Mathematics Championships