$x_{11}=$ amount shipped from Jefferson City to Des Moines $x_{12}=$ amount shipped from Jefferson City to Kansas City $x_{13}=$ amount shipped from Jefferson City to St$.$ Louis $x_{21}=$ amount shipped from Omaha to Des Moines $x_{22}=$ amount shipped from maha to Kansas City $x_{23}=$ amount shipped from Omaha to St$.$ Louis