Is that answer supposed to be the time when at least one machine was in use,
or when none were? My formula, see an earlier post, gave 348:15 and 160:15
respectively for those answers.
It wasn't obvious to me what your sheet was trying to do, nor what was
happening when the resolution was being changed. It didn't seem to converge
to a stable solution.
Hopefully the OP will be able to understand what each of us has done, and
whether either meets what he was trying to achieve.
--
David Biddulph

"Herbert Seidenberg" wrote in message
...
My answer: 159:48
http://www.freefilehosting.net/download/3c76e