I've used inkscape for the first time to make a map to put on the back of a business card. The map is finished and my problem is that after I save it according to the print shop standards (size and dpi), they say the map is still blurry. At one size it is clear, than the more I zoom out it gets really unclear. I saved it in a .jpeg format using GIMP.
I've spent literally hours trying to do different things to get it to work....

How can I get the map to be clear at the 90 mm x 57 mm size for the printers?
I'd appreciate any tips or advice anyone has to share!
Thanks!