To Calculate the Sum of Areas of Elements and Place as Text

Select the Area Calculator and Place Text tool (Drawing > Analyze > Area tools).
The Area Calculator and Place Text tool setting window opens:
Select the Green Plus button.
Select the first element and enter a data point out side the element to accept.
The element will be highlighted in green color. The area of the element will display at the top section of the tool setting window.
Select the second element and enter a data point to accept.
The element will be highlighted in green color. The area of this element will be added to the area of the first element and the sum of their areas will be displayed at the top section of the tool setting window.
Select the Place Text button.
Enter a data point where you wish to place the area text.
The sum of the areas of both the elements will be placed in the design.

Note: You can select multiple elements to find a sum of their areas.