The European Union has given Facebook two weeks to answer questions raised by the scandal over personal data harvested from the social network, according to extracts of a letter obtained by AFP on Tuesday. The letter EUs justice commissioner Vera Jourova sent Facebooks chief operating officer Sheryl Sandberg also asks what steps the firm plans to take to prevent a similar scandal in the future. "I would appreciate a reply in the next two weeks," the letter said.   "Have any data of EU citizens been affected by the recent scandal?" Jourova wrote, listing one of the five key questions. "If this is the case, how do you intend to inform the authorities and users about it?" Jourova asked.  Jourova asked whether stricter rules were needed for social media platforms as exist for traditional media and whether it would change its approach on transparency toward users and regulators. Facebook Inc Chief Executive Mark Zuckerberg plans to testify before US Congress, a source briefed on the matter said on Tuesday, as he bows to pressure from lawmakers insisting he explain how 50 million users’ data ended up in the hands of a political consultancy. Lawmakers in the United States and Europe are demanding to know more about the company’s privacy practices after a whistleblower said consultancy Cambridge Analytica improperly accessed data to target US and British voters in close-run elections.  Zuckerberg turned down British lawmakers’ invitations to explain to a British parliamentary committee what went wrong, Reuters reported. The company said it would instead send one of his deputies, suggesting that Chief Technology Officer Mike Schroepfer or Chief Product Officer Chris Cox had the expertise to answer questions on the complex subject. Christopher Wylie, the whistleblower who once worked at Cambridge Analytica, said on Monday that Canadian company AggregateIQ had developed the software that used the algorithms from the Facebook data to target Republican voters in the 2016 US election.