Dillards Inc., Little Rock, Ark., is merging its 401(k) plan with that of the former Mercantile Stores Co., which it acquired in August. The new plan will total $850 million. Merrill Lynch was selected to provide a range of plan services, including investment options and an education program with Internet access to the plan for the companys 70,000 eligible employees, according to Julie Bull, a Dillards spokeswoman. The number of options hasnt been determined yet, but all of the funds will be either Merrill funds or funds from mutual fund companies with which it has alliances, according to Wendell Wood Collins, Merrill Lynch spokesman. Merrill replaces Federated Investors, which had administered Dillards old plan, and Towers Perrin, which administered Mercantiles plan.