The head of Brazil's state-run oil giant Petrobras and five senior executives have resigned in the wake of a huge corruption scandal. Maria das Graças Foster's departure follows the arrest and testimony of some three dozen executives at Petrobras and many of its suppliers. The board of Petrobras is due to meet on Friday to elect new executives. The scandal involves alleged price-fixing, bribes and kickbacks, which implicates Brazil's ruling party. Prosecutors have uncovered around $800m in bribes and other illegal funds. More than 200 businesses are being investigated and more than 80 people, including three former executives from Petrobras,...