This is a fairly easy question on mensuration where you need to know the formula for the surface areas of a cuboid and a cube.
From the first statement of the question, we can make out that each brick is a cube of side 1.
The surface area of a cube of side ‘a’ is 6\(a^2\). Therefore, the surface area of one brick is going to be 6 square units.
The surface area of a cuboid of length l, breadth b and height h is 2(lb + bh + lh). The length of the given cuboid is 3, the breadth 2 and the height 2. So, the surface area of the given cuboid (solid brick) is 2(6 + 4 + 6) = 32 sq units.
From the above, we can also calculate that there are a total of 12 bricks. The total surface area of the 12 bricks will therefore be 72 sq.units.
The difference between these two is 40 sq.units.
The correct answer option, therefore, is B.
Hope this helps!