1. (Improved triangular substitutions; adapted from FNC 2.3.5) If B e RnXP has columns b, ..., bp, then we can pose p linear systems at once by writing AX = B, where X e RrXp whose jth column X; solves Ax; = b; for j = 1, ..., p. (a) Modify backsub.m and forelim.m from Lecture 13 so that they solve the case where the second input is an n x p matrix, for p > 1. (b) If AX I, then X = A-1. Use this fact to write a MATLAB function Itinverse that uses your modified forelim to compute the inverse of a lower triangular matrix. Test your function on at least two nontrivial matrices, that is, compare the numerical solutions against the exact solutions. 1. (Improved triangular substitutions; adapted from FNC 2.3.5) If B e RnXP has columns b, ..., bp, then we can pose p linear systems at once by writing AX = B, where X e RrXp whose jth column X; solves Ax; = b; for j = 1, ..., p. (a) Modify backsub.m and forelim.m from Lecture 13 so that they solve the case where the second input is an n x p matrix, for p > 1. (b) If AX I, then X = A-1. Use this fact to write a MATLAB function Itinverse that uses your modified forelim to compute the inverse of a lower triangular matrix. Test your function on at least two nontrivial matrices, that is, compare the numerical solutions against the exact solutions