It has six sides. Each face is exactly the same as the face opposite it, and the shape is exactly the same. So in fact, we only need to calculate the area of three rectangles and multiply it by two to get the total surface area.

Let's count them one by one. Simply put, it is width multiplied by length and then multiplied by two; Then the length is multiplied by the height, and then multiplied by two; Multiply the width by the height and then multiply by two.

Finally, the total surface area is obtained by adding the three results. Let's divide it into three steps.

To find the area of the upper and lower sides, we multiply the width by the length, which is the first part 2ab of the above formula, and bring in the value: 2ab=2*(4*5)=2*(20)=40.