The circle $C$ is defined by the equation $x^2 + y^2 - 6x + 8y - 11 = 0$. Determine the center and radius of the circle. Additionally, if another circle $C'$ is similar to $C$ but scaled by a factor of 1.5, find the radius of $C'$. Let's think step by step and output the final answer within \boxed{}.
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