Answer
$R=0$ ; interval of convergence is $(0,0)$
Work Step by Step
Let $a_{n}=n^{n}x^{n}$, then
$\lim\limits_{n \to \infty}|\frac{a_{n+1}}{a_{n}}|=\lim\limits_{n \to \infty}|\dfrac{(n+1)^{n+1}x^{n+1}}{n^{n}x^{n}}|$
$=\lim\limits_{n \to \infty}|(n+1)x(1+\frac{1}{n})^n|$
$=\lim\limits_{n \to \infty}|(n+1)xe|$
$=\infty$
Hence, $R=0$ ; interval of convergence is $(0,0)$