Shares of Dollar Tree Inc. rose 6.6% in premarket trade Monday, after the Wall Street Journal reported that activist investor Mantle Ridge LP has taken a $1.8 billion stake in the discount retailer and is planning to push it to take moves to boost its stock price. Mantle Ridge will push for changes at the company’s Family Dollar chain, the paper reported, citing people familiar with the matter. The investor is working with Richard Dreiling, former CEO of Dollar Tree rival Dollar General Corp. , who is credited with helping turn that company around in the early 2010s. Plans may include nominating directors to the Dollar Tree board when the one-month window to do so opens Nov. 24. Dollar Tree shares have gained about 40% in the past five years, while Dollar General shares have gained more than 190%.

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