Need Excel version: Telephone calls from New York to Los Angeles are transported as follows: First the call is sent to either Chicago or Memphis; then it is routed through either Denver or Dallas; and finally the call is sent to Los Angeles. The number of phone lines joining each pair of cities is as shown in the table below. Using a network flow model, determine the maximum number of calls that can be sent from New York to Los Angeles at any given time.

York to Los Angeles at any given time. TABLE 39 No. of Telephone Cities Lines N.Y. Chicago 500 N. Y.-Memphis 400 Chicago-Denver 300 Chicago-Dallas 250 Memphis-Denver 200 Memphis-Dallas 150 Denver-L.A. 400 Dallas-L.A. 350