Shares of CBS were up 4.6 percent in after-hours market trading, while those of Viacom Inc (VIAB.O), where Redstone is also chairman, rose 7.9 percent. Viacom’s board is scheduled to meet on Thursday, a company spokesman said, most likely to decide a successor to Redstone. CBS said Redstone would be replaced by Leslie Moonves, its president and chief executive since 2006.