TOKYO, March 25 : Oil prices dropped more than 5 per cent on Wednesday on the prospect of a possible ceasefire easing supply disruptions from the key Middle East producing region after reports the U.S. sent Iran a 15-point plan to end the war between them. Brent crude futures fell $6.21, or 5.9 per cent, to $98.28 a barrel by 0058 GMT, after declining to as low as $97.57. U.S. West Texas Intermediate (WTI) crude futures were down $4.67, or 5.1 per cent, at $87.68 a barrel, after falling to as