Draw the Network for This Assignment Problem

Draw the network for this assignment problem.
$$\begin{array} { l l } \text { Min } & 10 x _ { 1 A } + 12 x _ { 1 B } + 15 x _ { 1 C } + 25 x _ { 1 D } + 11 x _ { 2 A } + 14 x _ { 2 B } + 19 x _ { 2 C } + 32 x _ { 2 D } \\& + 18 x _ { 3 A } + 21 x _ { 3 B } + 23 x _ { 3 C } + 29 x _ { 3 D } + 15 x _ { 4 A } + 20 x _ { 4 B } + 26 x _ { 4 C } + 28 x _ { 4 D } \\\text { s.t. } & x _ { 1 A } + x _ { 1 B } + x _ { 1 C } + x _ { 1 D } = 1 \\& x _ { 2 A } + x _ { 2 B } + x _ { 2 C } + x _ { 2 D } = 1 \\& x _ { 3 A } + x _ { 3 B } + x _ { 3 C } + x _ { 3 D } = 1 \\& x _ { 4 A } + x _ { 4 B } + x _ { 4 C } + x _ { 4 D } = 1 \\& x _ { 1 A } + x _ { 2 A } + x _ { 3 A } + x _ { 4 A } = 1 \\& x _ { 1 B } + x _ { 2 B } + x _ { 3 B } + x _ { 4 B } = 1 \\& x _ { 1 C } + x _ { 2 C } + x _ { 3 } C + x _ { 4 C } = 1 \\& x _ { 1 D } + x _ { 2 D } + x _ { 3 D } + x _ { 4 D } = 1\end{array}$$