Plate with hole, mechanics problem

[Dafe]

Hey, I'm trying to solve a little mechanics problem and I'm stuck.

http://i163.photobucket.com/albums/t282/Calc_photos/PlateWithHole.jpg

I want to find the maximum stress in the system. I know that it should be at the top and bottom of the hole. The plate is fully constrained at the left edge.

I find the average tensile stress in section A:

sigma = F/A = 2000N/(100-40)*2 = 1,67N/mm^2

I also know that the stress distribution in section A is not even.

Could someone give me a little hint?
Thanks

[FredGarvin]

You're missing a 0 on the thickness for the area calculation. Once that is taken care of, you need the stress concentration factor that will be a function of the width of the plate and the hole diameter. That will multiply the average stress to get your peak stress.