AREA/CN (area/centroid) allows you to measure the area of 
a selected closed figure and displays the x and y 
coordinates of the centroid. Selected entity data 
information is always projected to the current display 
plane before area or centroid calculations are performed 
with the exception of the CIRCLE option.

Indicate the selection schemes for area and centroid
calculations by choosing from the following options:

CIRCLE   - to select an arc or circle for area and 
           centroid calculation.

CLSED LN - to select a set of line entities whose
           projections define a closed region in the 
           current view.

GENERAL  - to choose a set of entities (excluding points)
           whose projections define a closed region in the
           current view. Islands are permitted inside of
           the selected outer perimeter.
