Add mobile responsive feature to simple wordpress image plugin / Script

Hi. We have a simple wordpress plugin that is used to serve images to our other websites and now we want to have it mobile responsive. The original developer is quoting 16 hours to do this. It seemed way way to much to do this so I asked around. The original project was supposed to have this feature, but it slipped through the cracks. Here is a note from a close friend that does PHP, but doesn't have the time to do. **** "I’ve checked it. They have two files: [login to view URL] - 4000 lines very huge file, lot of work wnt into it more than 20-30 hours. But they didn’t made that file. It’s an external API. They’ve just downloaded it and used it uploadfiles-php - 500 lines around 400 if we remove empty lines. I can hardly belive that it took 16 hours for these 400 lines… that would mean, 25 lines/minute 2.5 minute for 1 line! Even if they think a lot, it is unrealistic. And some of these lines are just declarations, so a few seconds to do. So I would say around 8-10 if they have no experience. An experienced developer can do this in 3-5 hours. Clearly no 16 unless they’ve just learned how to develop. Btw these are the times for the full development. If they just changed it to work with mobile it’s impossible. Maximum 3 hours! Or 5 if they’re very bad :D. So I would say they are not legit." **** So please send me an honest bid to add mobile response to this plugin. If you need more info I will send you a few screen shots of this plugin.