Marine pleads guilty in Merced death, is finedSAN FRANCISCO (UPI) — Marine G«MerySgt. Edgar Post has pleaded ; nitty to charges of negligent ~ ioakkfe and dereliction of duty• weal tint from a erenade explosion - which killed a young security guard inMerced.; Pott, 38. a veteran of JO years in the• Marines, entered his pie* yesterday just before the start of his special court martial at the Treasure Island 'Navy Base.He was fined $1,500 and will also be . given a letter of reprimand..* Lewis Anderson, 18, died a weekafter a white phosphorous grenade exploded as he examined it in a storage shack behind the shopping mall on July 2*. The grenade had been part of a Marine recruiting display.Investigators said several other rounds of ammunition in the display were also found to have been live.” They included a (Omm mortar round, a lWrora howitzer - primer and 25 rounds of rifle ammunition.Post had been in charge of the display for Company K, 3rd Bat-tlatkm, 23rd Marines, a Stockton reserve unit.