I am a non-programming user who is learning model builder for the first time. I've had success creating my initial workflow, but am having trouble calculating a field, based off of other fields already present in my polygon layer. The calculation is simple, multiplying one field by 2, and dividing the product by another. When I verify and run, I get the "Item not found in this collection" error. I have attached the .py file, and appreciate any advice! Thanks!