The Chinese currency Renminbi, or the yuan, strengthened to a record high of 6.4399 against the US dollar on Monday, according to the China Foreign Exchange Trading system. In China\'s foreign exchange spot market, the yuan is allowed to rise or fall by 0.5% from the central parity rate each trading day. The central parity rate of the yuan against the US dollar is based on a weighted average of prices before the opening of the market each business day, according to China\'s (Xinhua) news agency. (QNA)