Especially C. You have someone who likes software you've written for them and is apparently good at doing business with trade shows. Probably there is other so

Especially C. You have someone who likes software you've written for them and is apparently good at doing business with trade shows. Probably there is other software which would be useful to participants at trade shows he could sell more of. Just don't be especially surprised if his answer is that whatever he charges the trade shows covers an awful lot of manual work, setting things up, contact the other parties et cetera and the software is just a small but necessary part of that.