ASHINGTON, Jan. 30 — The White House strongly defended the new Medicare law offering prescription drug benefits and private health plans to the elderly today, despite projections that it might cost at least $530 billion over 10 years, or one-third more than the price tag used when Congress passed the legislation two months ago."The Medicare reform we did is a good reform," President Bush said in a brief exchange with reporters. "It fulfills a long-standing promise to our seniors."Mr. Bush did not directly answer a question on whether he was worried about the reaction of conservative Republicans who voted for...