The general rule of thumb is 10% of the production budget and is usually worked out to be roughly $2,000 a week.
$6,000-$10,000 for projects under $100,000
$10,000 for projects over $100,000
If it is a low budget or corporate film, perhaps the below would be a good place for a producer to start:
Pre/Post Production Day $750
Half Pre/Post Production Day $450
Writing - $85 per hour
Or minimum of $450 as a piece rate