$J$: Model
$t_{i,j}$:Time for $i$ to produce $j$ $\;\forall i, \forall j$
$P_j$ Price
$q_j$ Demand
###Model
Var $x_{i,j}$ $\;\;\forall i\in I\forall j\in J,\;\;\; x\ge 0, x\in Z$