Let $x_1,x_2,$dots,$x_n$ denote a random sample from the probability density function

$f_x(x$;$,)=\{\begin{array}{cc}\frac{1}{(){}^{}}{x}^{-1}{e}^{-\frac{x}{n}},& x>0\\ 0,& \text{e}\text{l}\text{s}\text{e}\text{w}\text{h}\text{e}\text{r}\text{e}& \end{array}$

a$)$ Find the method$-$of$-$moments $($MOM$)$ estimators of $$ and $.$

b$)$ Find the method of maximum likelihood $($MLE$)$ estimator of $$ when $=3.$

c$)$ Find the sufficient statistics for $$ when $=3.$