Sheldon wrote:
>
> A basic starting point is to double the time for two items, triple the
> time for three [items] and so on

This is what I thought. However, this isn't a good idea. Most people
have cheap microwave ovens that aren't particularly up to the task of
cooking for long periods of time. My own inexpensive -- heck, nearly
disposable -- microwave oven heats up like a radiator after six
minutes, so I hardly want it running for twelve. I cook just about
everything one at a time.