37% disapprove. there are reports one of gadhafi s sons has been killed but taking him out is not on the agenda, says secretary of state hillary clinton. estimates put the cost of u.s. involvement in libya at $100 million to $300 million every week. jim aceda is in tripoli with the latest. reporter: for the fourth night tripoli was hit by a wave of cruise missile strikes on the capital, triggering another barrage of anti-aircraft and tracer fire. u.s. military officials say the offensive has effectively taken out libya s air defenses including these multiple rocket launchers at tripoli s naval base which foreign reporters were allowed to visit. libyan officialed insisted this facility was only used for training and repairs and the air strikes have not put a dent in moammar gadhafi s defiance. speaking to supporters from his palatial compound last night he called the nato led coalition a