Corporate rates for press campaigns

I was apporached by a large corporate recently to write a short press feature, as their usual consultant was not available. It was a lucky break for me, as they've apporached me again for more work. The company wants to re-use the original press feature in various publications, and as we did not have a contract drawn up, I am unsure of the procedure around payment for the re-use of work. They have asked me what it will cost them to re-use the piece, tailored of course to the different publications. Any advice would be appreciated.