If f(x)=∑cnxnf(x) = \sum c_n x^nf(x)=∑cnxn has radius R=5R=5R=5, what is the radius of g(x)=f(2x)g(x) = f(2x)g(x)=f(2x)?
R=5R=5R=5
R=2.5R=2.5R=2.5
R=10R=10R=10
R=7R=7R=7