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What: Shares of cardboard packaging maker RockTenn (NYSE: RKT) have gotten crushed today, down to the tune of 10%, after the company posted first-quarter earnings last night.

So what: Revenue summed up to $2.27 billion, resulting in adjusted earnings per share of $1.18. Both top and bottom lines were shy of consensus estimates, which expected $2.31 billion in sales and a $1.40 per-share profit.

Now what: The growth in revenue was mainly attributed to RockTenn's acquisition of former rival Smurfit-Stone last year. The company continues its process of digestion, with net costs associated with restructuring and transitioning adding up to about $0.12 per share after tax. Most of these costs were related to plant closures and other integration costs.

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Fool contributor Evan Niu holds no position in any company mentioned. Click here to see his holdings and a short bio. The Motley Fool owns shares of RockTenn. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.