I was on the same vein, but the petroleum and fish exports doesn't really fit so I was thinking UK first. In retrospect though I wasn't considering the total trade value, it narrows possible countries quite a bit, could make it a bit too easy maybe? It's probably a lot harder though with less prominent countries. Why only one per day though!

I actually missed the significance of the arrow entirely. It's obvious but I still focussed mostly on the distance.

Germany immediately was not an option... Volkswagen alone has like 100 Bln revenue per year.