Exercise 1 Write a Matlab program that returns the numerical solution to the upper triangular system of bi b2 0 u22' T2 .(n-1)n bn 00n by using the backward substitution algorithm. The function name, inputs and output are given below function x] backward sub(U,b) Input: U: upper triangular matrix b: column vector representing the right hand side of (1) Output: x: solution to the linear system (1) (column vector)