There is no model for us to shade in
In a parallelogram, opposite angles are congruent.
This means that the four angles of the parallelogram are:

Moreover, the sum of the interior angles of a polygon with n sides is 180(n-2). So, the sum of the interior angles of a parallelogram is 360.
This means

And since
, we have 
Answer:
5n units
Step-by-step explanation:
C=2πr =2·π·2.5