Hudson's Bay Co. agreed to buy discount retailer Kmart Canada Co. for $168 million, including debt, and will fire 4,000 to 6,000 employees after it combines the newly acquired business with its Zellers chain. Toronto-based Hudson's Bay, Canada's largest retailer, said it will merge its 298 Zellers discount stores with Kmart Canada's 112 locations and close more than 40 of the combined companies' stores. The dismissals represent as much as 8.6% of the 70,000 workers Hudson's Bay will have after the transaction. The acquisition eliminates Hudson's Bay's smaller discount rival, leaving Wal-Mart Stores Inc. of the U.S. as the only other major discounter doing business in Canada. It also gives a boost to the poorly performing Zellers chain, which has been losing sales to Wal-Mart, the world's biggest retailer.