CAIRO - EgyptKuwait Holding's stock tumbled 9.7 per cent on Sunday after its chairman, Kuwaiti billionaire Nasser al-Kharafi, died while on a trip to Cairo. Kuwait's state news agency KUNA said on Sunday Kharafi had died after suffering a heart attack. An earlier report from Al Arabiya television said he died on Saturday. The firm has yet to announce the death officially.