I think it is two. I’m sorry if I am wrong.
41 and 5/8ths feet is for one rectangular garden, and 166 and 1/2 feet is for all four gardens combined
Distribute the first +a to the +a and multiply, then multiply the same +a and the +b and then multiply the -b and the +a and then the -b and the +b.
Hope this helped, if you have any more questions about this, just ask.