1. Assume that a computer solves a 900-variable, upper-triangular, linear system by back sub- stitution in 0.2 seconds. Estimate the time needed to solve a general (full) linear system of the same size by Gaussian elimination (LU-factorization). You could do this problem using the counts n3 + O(n2) for Gaussian elimination (GE) and n2/2+O(n) for backward substitution stated in the book, or the counts from class: 2n3/3+ O(n?) for GE and n for backward substitution. Use the later counts. 1. Assume that a computer solves a 900-variable, upper-triangular, linear system by back sub- stitution in 0.2 seconds. Estimate the time needed to solve a general (full) linear system of the same size by Gaussian elimination (LU-factorization). You could do this problem using the counts n3 + O(n2) for Gaussian elimination (GE) and n2/2+O(n) for backward substitution stated in the book, or the counts from class: 2n3/3+ O(n?) for GE and n for backward substitution. Use the later counts