Please solve using excel solver only Answer should be 750

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. Cities # of Telephone 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 Hint: Treat each pair of cities as a capacitated arc and maximize the number of calls that can be made from the origin to the destination Difficulty Level: Medium