BEIJING (Reuters) - China promised on Monday to respond positively to the United States in high-level economic talks this week but drew a line in the sand by telling Washington that its exchange rate is a matter of national sovereignty.	TOKYO -- Nissan Motor Co. announced plans Monday to launch a next-generation fuel cell vehicle in the early 2010s in Japan and North America as part of its mid-term environmental strategy.	Metro faces a $116 million budget shortfall the next fiscal year, raising the possibility of fare increases, reduced bus and rail service and higher contributions from area taxpayers, according to budget documents and interviews with board members.
The Federal Trade Commission yesterday said that companies engaging in word-of-mouth marketing, in which people are compensated to promote products to their peers, must disclose those relationships.	Former Enron chief executive Jeffrey K. Skilling received at least a brief reprieve from prison yesterday after a federal appeals court said it needed more time to consider whether he should remain free pending appeal.	The Post's Amy Joyce offers advice about gracefully managing interpersonal issues on the job.