Article Writing - Unique articles required(repost)

I require unique articles to be written for a client of mine. The articles will have to be around 350-500 words each and should ideally be broken down into 4-6 paras each. I'll be giving you the details of the website for which the articles need to be written as well as the keywords that should be used while crafting the articles once the project is awarded. The tone of the articles should be informative/educational, but at the same time there should be subtle promotion of the site as well. So for e.g. If we talk about a certain feature or service in general, after stating the feature/service we also say that we have it in our offerings and why someone should opt to do business with us. The requirement is on an ongoing basis and hence the project might be awarded to more than 1/2 parties. Also, we'll be focusing on quality aspect so please only bid if you are sure you can deliver good quality articles which are not plagiarized. When you submit your bid, please submit the cost for a single article. To start with we need a batch of 20 articles. The project is ongoing and we might also consider offering article rewrite services.