Need help with FOV area (mm2) totally confused?

im confused i have the FOV diameter they are:
4x = 5
10x = 2
40x = 0.5

a classmate told me she thinks the area for 40 x is:
pi(5/2)^2 = 19.6
not sure if that's true or how to do it for the low and medium, magnification.
please help its due in a few days!

Similar Questions
    1. answers icon 2 answers
  1. 1. She was confused at his error.1-2. She was confused by his error. 2. He was confused about something. 3. He is confused in
    1. answers icon 1 answer
  2. I totally don't understand VectorsHow do you describe a vector as an ordered pair? on the x and Y where they cross it is 41
    1. answers icon 1 answer
    1. answers icon 3 answers
more similar questions