Forest fire control organizations in Canada’s provinces6 must reposition the numbers of observation aircraft available at stations i = 1,

c, 11 on a daily basis to adjust for changing fire threats.

The required number ri and the present number pi are known for all stations, along with the cost ci,j of moving an aircraft from any station i to station j. Explain how the problem of choosing a minimum total cost plan for repositioning aircraft can be modeled as a transportation problem by identifying the sources, sinks, supplies, demands, and arc costs.