Jim Cramer answers viewers' Twitter (TWTR) questions from the floor of the New York Stock Exchange. He weighs in on Alcoa (AA), stressing that what the Alcoa investors want is the Alcoa after the merger with RTI International Metals (RTI), so that the company is expanded beyond just aluminum. Cramer says you're not going to get a pop in this stock until that deal closes, because these days, a company can't just be an aluminum-maker. He explains that the Alcoa he likes is the future company, not the present version of it. Another viewer notes that after reaching $90 a share, Shake Shack (SHAK) looks like it's heading down to $60, and asks for Cramer's long-term view on the stock. Cramer says he likes it long-term as he believes in founder Danny Meyer and thinks the burgers are terrific. However, he urges investors to realize that it is over-valued per store when you compare it to other burger chains like Jack in the Box (JACK) and McDonald's (MCD). Even though he believes Shake Shack is better than those competitors, it's still overvalued. If you have a stock question, tweet it @jimcramer using #CramerQ.