June 2012 Question 1

I assume you are meaning the machine costs? (There are lots of costs, although most of them are specific.)

Part of the machine cost is fixed and so that does not change. The rest is variable, but based on the number of batches.
At the moment they make in batches of 500, which means there are 80,000/500 = 160 batches.
They are changing to batches of 400, which means there will be 80,000/400 = 200 batches.

That should sort you out with regard to the machine costs. If you were meaning one of the other costs, then if you say which one then I will try and help.