Lightning Round: Don't know why this is so cheap

It's that time again! The Lightning Round bell has rung, and Jim Cramer gives his take on a few favorite audience stocks:

Rackspace Hosting: "You do not buy stocks with declining fundamentals hoping that there will be a takeover. I say don't buy."

Cowen Group: "Frankly I don't understand why this stock is so cheap. It's down, it's a buy and I think it's a good organization. A lot of those broker stocks are moving, and that one should move with it."

Merrimack Pharmaceuticals: "We've been liking Merrimack as a spec, we think it's in good shape. That's a good one to be in."

Cummins, Inc: "I believe that China is turning. Therefore I cannot be negative on Cummins. They're a great Indiana company, I want you to buy it."

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TrueCar: "No, I like CarMax and I like AutoNation."

VCA Inc: "We spend a fortune on our pets, we love our pets, don't we? And we are a buyer."

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