This excellent essay was recently published in the Kitchen Gardeners International (KGI) newsletter.
The calculations below are exactly why I'm promulgating that we all need to stick a few seeds in the ground for our friends and neighbors who are going through a rough time. Donating a few dollars to a food bank is a good idea. Donating hundreds or thousands of dollars worth of food is a great idea.
Isn't that a great photo? Kitchen Gardeners Int'l is a great website with lots of great info. I encourage you to sign up for their e-newsletter, as I have.