Leontief Tableau Économique (produit net) I’m doing some practice questions and I found this one about calculating produit net. I know that produit net or surplus is the amount that has to be paid to the landlords, and which becomes available at the start of the whole process all over again. 

I also know that 1/2 of the expenditure revenue goes to the productive sector (farmers) and 1/2 goes to the sterile sector. Farmers produce 100% of it, and the sterile sector sends 50% to the farmers. Basically a zig zag table. 

My questions: what does the attached table mean (why is there a purchasing industry and a producing industry), and what is the produit net? 

Thanks
In this transaction table, farmers produce 5 as a producing industry and consumes 2 (out of 5) as a purchasing industry. This means that they retain 2 as food for themselves and sell the remaining. 

A hint: The physiocratic "net product" is equivalent to agricultural rent payment.