题目the company needs to make plans for the energy systems for a new building. The energy needs in the building fall into three categories:(1)electricity (2)heating water (3)heating space in the building.The daily requirements for these three categories(all measured in the same units)are Eletriciy 20units Waer heating 10units Space heating 30units The three possible sources of energy to meet these needs are eletricity, natural gas,and solar heating unit that can be installed on the roof.The size of the largest possible solar heater to 30 units,but there is no limit to the electricity and natural gas available.Electricity needs can be met only by purchasing electricity at a cost of $50 per unit.Both other energy needs can be met by source or combination of source.The unit costs are electricity natural gas solar heating Water heating $90 $60 $30 Space heating $80 $50 $40 The objective is to minimize the total cost of meeting the energy needs. 我解答至 ele wat spa 最低需求 最高需求 ele 50 90 80 20 M gas M 60 50 0 M solar M 30 40 30 30 total 20 10 30 60 但解答 ele wat spa 最低需求 最高需求 ele 50 90 80 20 60 gas M 60 50 0 40 solar M 30 40 30 30 total 20 10 30 60 想请问..解答的最高需求40和60是如何判断的? --

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