Exploration $3\mathrm{.}1\mathrm{.}4$ Modify your script from Exploration $3\mathrm{.}1\mathrm{.}3$ to solve a general upper triangular system of three equations in three unknowns $x,y$ and $z.$ Assume that the coefficients of the system are stored in a $33$ matrix $U,$ and that the right$-$hand sides of the equations are stored in a $3-$vector b$.$ Test your script on a randomly generated $U$ and $b,$ using MATLAB's backslash operator to check your solution.