ZAMBIA'S KWACHA FALLS AT WEEKLY AUCTION The Zambian kwacha fell at this week's foreign exchange auction to 18.75 kwacha to the dollar from last week's 16.95, the Bank of Zambia said. The rate was the lowest since the auctions resumed two weeks ago under a new two-tier exchange rate system worked out with the World Bank and International Monetary Fund. The Bank of Zambia said it received 370 bids, ranging from 13.00 to 20.75 kwacha, for the six mln dlrs on offer. One hundred and thirty-five bids were successful. A British High Commission spokesman said Britain would put eight mln stg into the auction at a rate of one mln a week as soon as Zambia reached a full agreement with the IMF. The money could be spent only on goods produced and supplied by British firms, excluding luxuries and defence equipment, the spokesman added.