$(10$ pts$.)$ Use the Gauss$-$Seidel method to solve the following system until the approximate relative error falls below $lo{n}_A=0\mathrm{.}0005.$ If necessary, rearrange the equations to achieve convergence.

$-3x_1+x_2+12x_3=50$

$6x_1-x_2-x_3=3$

$6x_1+9x_2+x_3=40$

a$)$ using a built$-$in function in matlab $($linsolve$)$

b$)$ using a matlab script that you write.

c$)$ what goes wrong, if anything, if the equations are not reordered?