# help needed

• Jul 5th 2010, 12:28 PM
hsojua
help needed
http://www.mathhelpforum.com/math-he...g-mathhelp.jpg

• Jul 5th 2010, 12:38 PM
hsojua
so far i have an objective function

obj = f*28 + a*f*32 + 0.4*a*f*45 - 0.1*a*f*190 + c*0.5*a*f*25 + d*0.5*a*f*35 + b*f*31 + 0.37*b*f*45 - 0.08*b*f*210 + c*0.55*b*f*25 + d*0.55*b*f*35 - 0.2*c*0.5*a*f*210 - 0.4*c*0.5*a*f*175 + 0.4*c*0.5*a*f*45 - 0.3*d*0.5*a*f*175 - 0.4*d*0.5*a*f*190 + 0.3*d*0.5*a*f*45 - 0.2*c*0.55*b*f*210 - 0.4*c*0.55*b*f*175 + 0.4*c*0.55*b*f*45 - 0.3*d*0.55*b*f*175 - 0.4*d*0.55*b*f*190 + 0.3*d*0.55*b*f*45

where f = feedstock in tonnes
a,b,c,d are all percentages

the waste bit just seems to go round in circles so dont know how to put that into the objective function
eg. process c produces 0.4 tonnes of waste which goes into process r which produces 0.4*0.3 tonnes of intermediary which goes back into either process c or d producing yet more waste
• Jul 5th 2010, 03:15 PM
HallsofIvy
Since "waste product cannot be disposed of by the plant" it generates no profit and so has no place in the objective function which should be "total profit".
• Jul 5th 2010, 03:26 PM
hsojua
it costs money to go through process r which all waste has to in order to be disposed so it does need to be in the objective function as i am trying to maximise profit which is revenue - costs