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When in FireFox, navigate to print by selecting the three-horizontal-bars settings icon, and select the Print icon.
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Install them one at a time, sending a test print page to each. If any of your printers are missing, select "Add Printer", and Windows 10 will produce a list of printers that it finds. If the default is other than the printer you wish to print to - right-click your preferred printer, and select "Set as default". To send a test print to a printer, right-click its icon, and select "Printer Properties", then click on the "Print Test Page" option button. If you have any with two or more copies, you might have to test which one works best, and remove the other(s). Make sure that all your printers show in there. See what printer is set as the default (its icon will have an overlay of a green circle with a white checkmark). Have a look in "Devices and Printers" in the Windows 10 Control Panel.
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