I have been reading the paper of Acemoglu et al., 2016 [Networks and the macroeconomy : an empirical exploration][1]
Networks and the macroeconomy : an empirical exploration, and I have been struggling with a maximization programm in the early pages of the article. Even if I get the following parts, I am a bit frustrated I can't prove one of the first results.
The production function is :
With $x_{ij}$ the products of the firm $j$ treated as input for the output of the firm $i$.
My question is the following : What should I take as constraint for my Lagrangian function ? I am having difficulties seeing how the authors came to the (4) conclusion :
I think the constraints is given by the relation
But I must admit I am not sure about my result with these constraints.
Could anyone give me a tip about the constraints and how to proove the $(4)$ relation ?