Write a Matlab function that computes the following sum while requesting the value of $x$ and $n$ from the user.

$y={\displaystyle \underset{k=1}{\overset{n}{}}}(\frac{2}{x}{)}^k$

To call the function, the user should use the following

$b{\displaystyle \underset{?}{\overset{?}{}}}(x,n)$