Since the upgrade to Sierra, Firefox defaults to double sided printing. A clean uninstall and reinstall of Firefox now lets me select single sided printing and it will do so (which it wouldn't before: only printed double sided even with single sided selected), but it would be more convenient to not have to select single sided each time I print a web page. All other apps on my Mac default to single sided printing, so the problem seems to be with Firefox. How can I set the default to be single sided, vs double sided printing on my Mac?