...our supply decision. MRSt denotes for the marginal rate of substitution between labour and consumption. We assume that labour markets are competitive and also that individuals work in each sector z 2 =-=[0; 1]-=-. Therefore, Lt corresponds to the aggregate labour supply: Lt = Z 1 Lt(z)dz: (2.5) 0 42.2 Firms 2.2.1 Final good producers There is a continuum of …nal good producers of mass one, indexed by f 2 [0;...