3 articles a week, monthly price needed

Hi there, I have three sites. 1. sells electric hand dryers targeted clients are pubs, restaurants, bars, schools, hotels, gym, fast food shops etc. 2. sells projectors, projector screens, interactive whiteboards targeted clients are home cinema and game consoles users, schools and conference rooms for interactive screens. 3. sells cctv cameras and intruder alarms targeted clients are residential premises, business premises, schools etc wherever security is an issue. I need one blog wring for each site every week. So 3 blogs a week. These blogs should be written SEO optimized and targeting our clients and must be relevant to our niche. I need regular work and posting them to our website. You must use meta title, description and keywords related to the article. Anyone native English speaker would be ideal for this job or someone with very good English writing and understanding of our products is also suitable. You must give me prices for 12 articles a month as its 3 articles a week. I look forward to your replies. Many Thanks