Send any friend a storyThe group of major oil-producing countries known as OPEC Plus agreed on Sunday to embark on a complex effort to adjust production as it aimed to halt the recent slide in oil prices, including an additional cut in output of one million barrels a day by Saudi Arabia. With oil vital to the economies and governments of many of these countries, it was not surprising that the tricky issue of addressing quotas produced a meeting that ran well into the evening in Vienna. With OPEC Plus producing more than 40 percent of global oil supplies, the group can exert considerable sway over markets if it tries hard enough