So last year I was working for this company and worked there for about 13 months. I was hired as a web dev but was soon moved on to creating web banners in html5 so that a friend who was doing that before could focus on design for prints. Well few days ago that friend called and said he was going on a vacation and was wondering if I would like to come back an fill in for him while he is on vacation.

Since the company can't find anyone willing or that did that job before and nows all the specs like I do I was their only choice for the job (yaay me). Of course I accepted the position as it wouldn't require me to be in their office from 9-5 but only on certain days when banners need to be created and for few hours only.

The downside of this is it will last for a whole month (didn't expect that) and it poses a chance to conflict with my current job. But my current boss is ok with me doing this as long as my "day job" doesn't get affected.

So now that I know I'm their only choice for the position and they don't have time to look for someone else and train them as the friend already left for vacation.

What do you guys think, how much should I charge them for this work ?

They are still waiting for my quote on the price.

I'm thinking of a fixed price for 1 month of work and somewhere around 600€ minimum.

My salary while working for that company full time was 400€ and I did web dev + banners (static and dynamic).

On a side note:
I heard from a few friends who still work there, that they might offer me full time job there again. But that is a whole new rant for another time