I'm in Stockholm, and in a few days I'll have to travel to the Arlanda Airport.
My question is the following: I have some balance on my SL card. The SL site mentions a specific ticket for the airport (at least I need a zone C, and also the airport fee); when I travel to the airport, I will have to take the bus, and then the train to Arlanda. When I first scan the card at the bus, will I have to pay another SEK 25 on top of the train's cost? And when I take the train, how do I indicate that I'm travelling to zone C?