Problem 4 a Use a single-precision routine for Gaussian elimination to solve the system Axbdefined below 21.0 67.0 88.0 73.01 X11 141.0. 76.0 63.0 70 20.0109.0 0.0 85.0 56.0 54.0||x31 1218.0 19.3 43.0 30.2 29.4JL 93.7 b. Compute the residual rb - Ax using double-precision arithmetic, but storing the final result in a single precision vector r. (Note that the solution routine may destroy the matrix A, so you may need to save a separate copy for computing the residual.) c. Solve the linear system Azto obtain the "improved" solutionx d. Repeat steps b) and c) until no further improvement is observed z. (Note that the matrix A need not be refactored.)