Easy (assuming no major delays, needless to say). As for the bag, most of my connections through CPH over the years were in the region of 40/50 minutes (often even shorter, mostly due to wintry weather) and I've never had any issues (so far at least, touch wood). Things, however, could go wrong and you clearly need to plan accordingly, especially if one looks at your travel arrangements with a number of flights 'squeezed' in such short period of time (and I'm assuming you will be travelling to SIN on separate tickets). That said, I am sure somebody will be able to advise on whether SK would be in a position to deliver your bag to Singapore should anything go wrong on your way to ARN. Again, though, 45 minutes at CPH would be a walk in the park (in normal circumstances).

G