Answer:
42a²
Explanation:
Let the edge be a. Ten cubes stacked means 4 vertical edges of the cubes are 10a each. The four sides have the total area of 4 x 10a x a = 40a²
The base and top of the cube are square, so the area of the base and top each is a².
The total surface area of 10 cubes stacked = 40a² + a² (base) + a² (top) = 42a²