The standard maximum size of the image that can be printed is 640 x 480 pixels or 2.133 inches by 1.6 inches at 144 dpi. You can upsample the resolution of the image to 300 dpi, with a program like Adobe PhotoShop, but the image remains the same dimensions. The other thing you can do is increase the dimensional size of the image to 6.75 x 9 inches and keep the resolution at 144 dpi or increase it to 300 dpi. The line screening is independant of the dots per inch. It can have 80-lines per inch or 150-line or 175-line screens, and it only matters if you are creating a CMYK separation to an image setter, instead of to a continuous tone color printer. The lines per inch you would choose would have to do with the type of paper you print on.
Support Information Services