When the height of a cuboid is 8 cm, its bottom is a square with a side length of 3 cm, So how much is the feature volume increased?

When the height of a cuboid is 8 cm, its bottom is a square with a side length of 3 cm, So how much is the feature volume increased?

The original volume is 72cm ^ 3 and the area is 114cm ^ 2
Later it became volume (a + 3) ^ 2 * 8
Area 2 * ((a + 3) ^ 2 + (a + 3) * 8 * 2)