$4($a$)$ The normalised LMS algorithm is described by the following recursion for the weight vector $R_x=\left[\begin{array}{cc}1& 0\mathrm{.}5\\ 0\mathrm{.}5& 1\end{array}\right].$ Define the range of values for the learning rate parameter $$ of the LMS algorithm for it to be convergent in the mean square sense.