Doesn't sound like you need solver for this

You need to lift the total liquid produced in 21 days

that has a fixed cost of .42/bbl x amount of liquid (measured in bbl) you
produce in 21 days.

the only cost depending on when you lift the liquid is the $5 fixed cost.
So you obviously want to minimize the number of lifts - each one you
eliminate saves $5 or conversely, each one you perform costs $5.

Thus you lift Max - Min gallons each time. That would be Production in
21 days/(max - min) to identify how many lifts.

the only variability would be the start volumne and end volume. the first
lift would start at (Max-Start volumn)/production rate. then you would
space out the calculated number of lifts and deal with the last few days if
you have some target volumn you need to end with.

--
Regards,
Tom Ogilvy

"deano" wrote in message
ups.com...
KISS : keep It Simple Sam. This is a revised request to help on a
period solver to schedule lifts

You have a tank that contains liquid. You make liquid each day at some
rate. The tank has to hold this daily make. Tank has a max and a min
volume of liquid to hold. You have to lift liquid out of tank so that
it stays within main & max. It costs $5 + $0.42/bbl to lift liquid out.
You know how much liquid you have in tank to start and how much liquid
make for the next 21 days. what is the optimal lift schedule. See the
solver & click show scenarios available here
http://availg.com/images/stories/tools/runout_1.xls

Problem: why is solver not finding the optimal schedule of lifts
regardless of initial guess?

For Example:
go to model tab:
click show scenarios
select base then close
go to Tools solver
click solve
solve does not find optimal schedule.

click show scenarios
select optimal then close
That is the optimal solution.

Your help is greatly appreciated.