Rick Gates, the former campaign aide to Donald Trump, is cooperating with Special Counsel Robert Mueller’s probe into whether individuals from the Middle East worked with the Trump campaign to influence the election, according to two individuals with first-hand knowledge of the investigation. Gates has answered questions specifically about Psy Group, an Israeli firm that ex-employees say drew up social media manipulation plans to help the Trump campaign, according to sources familiar with the questions. Mueller’s team also asked Gates about interactions with Psy Group’s owner, Joel Zamel, and Lebanese-American businessman George Nader, who worked as an emissary for Saudi...