Someone told you the LU decomposition of a non-singular A € Rnxn (assuming for simplicity that the Gauss-Jordan process required no permutations) and gave you b € Rª. Describe how to solve Ax b in only O(n²) arithmetic operations given this information. Modify your algorithm to handle the general case, i.e. when A = PLU is given (P ‡ I). =