FRANKFURT (Reuters) – Germany’s RAG foundation has written off all of its investments in Rene Benko’s insolvent Signa Group, RAG Chief Executive Bernd Toenjes said in an interview with Frankfurter Allgemeine Zeitung published online on Tuesday. “That amounts to between 1-2% of our total assets, so it is still a manageable proportion, but it is annoying – one does not like taking steps like that,” Toenjes told the German newspaper. With the foundation’s assets currently totalling 17.6 billion euros, this amounts to between 180 and 350 million euros, the report said. Property and retail giant Si…