4.4 Forest scheduling problem Paper and wood products companies need to define cutting schedules that will maximise the total wood yield of their forests over some planning period. Suppose that a company with control of m forest units wants to identify the best cutting schedule over a planning horizon of k years. Studies that the company has undertaken predict that forest unit i will have wij tons of wood available for harvesting in the jth year. Based on its prediction of economic conditions, the company believes that it should harvest at least 1; tons of wood in year j. Due to availability of equipment and personnel the company can harvest at most uj tons of wood in year j. Formulate the problem of determining a schedule with maximum wood yield as a network flow problem. Note: It is assumed that wood harvested in any year will not regrow in within the planning horizon of k years. Furthermore, it is assumed that l;