Jim Cramer's Lightning round: Petrobras, Alcoa, Merck and more

Here are some calls "Mad Money" host Jim Cramer made on stocks viewers asked about.

US Airways: If the US Airways-American merger goes through, Cramer thinks LCC could rise to $30 a share.

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Rambus: It's time to take profits on this stock, Cramer said.

Matador Resources: Go with rival EOG Resources instead, Cramer said.

Petrobras: Cramer continues to like this oil stock.

Alcoa: The aluminum maker's stock has been climbing slowly, Cramer said. He's a buyer.

Merck: This pharma lacks a vision right now, Cramer said. "Don't buy."

ConocoPhillips: Cramer called this a terrific stock.

United Rentals: This stock could go to $80 a share before Cramer would consider it expensive.

Call Cramer: 1-800-743-CNBC

Questions for Cramer? madmoney@cnbc.com

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