Answer and explanation:
The surface area of a solid is the sum of the areas of all faces of the solid. The surface area of a cube is calculated using the formula 6a² since a cube has 6 faces in total likewise a cuboid.
We can say the rectangular solid is a cuboid and to find the surface area of the cuboid we add up the surface area of all 16 cubes
Surface area is therefore 16×6a²
