Because you seem to have an understanding of the material, I will write my math, but no explanations for my work. Comment on this answer for an explanation, or if I did something wrong.
1. Find the length of the South side of the field.

2.Find the perimeter of the pumpkin field.

3. Find the perimeter of the whole field.

4. If
, what is the total perimeter?

Random Tangent:
If you want to involve
in finding these answers for whatever reason, your math is going to get messy. Here's what I tried before I realized you could multiply each side by
to get the total perimeter:

Now the other side. This one's even worse.

At this point, was realizing I wasn't going about the problem correctly, but did one last try by setting
. At this point in the equation, I simply had to stop, both due to complexity and technological problems.

I could possibly continue to solve, but I don't see a point. It was clear that this was NOT the right path to take finding the perimeter. It was here I realized that I could just multiply the two sides without
in them by
and--without as much difficulty--reach the correct answer.