"To wrap up the first iteration, we calculate our final trip values. For T {2 3}, we use the production of 2,000 for Zone 2 and the attraction of Zone 3. This gives us 1,429 trips.Now, look at Zone 3. Since the productions (P 3) for this zone are zero, it doesn't matter what the attraction or friction factors are—the entire third row of our matrix becomes zero. No trips are originating from Zone 3.With the matrix filled, let's evaluate our results. This is the A {computed} vs. A {given} check.I