Problem 4 a. Use a single-precision routine for Gaussian elimination to solve the system Ax - b defined below 21.0 67.0 88.0 73.01X11 141.0 76.0 63.0 7.0 20.0x2 109.0 0.0 85.0 56.0 54.0x3 19.3 43.0 30.2 29.4 JLx4] L 93.7 x3218.0 b. Compute the residual r b-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 Az = r to obtain the "improved" solution x + (Note that the matrix A need not be refactored) d. Repeat steps b) and c) until no further improvement is observed