Problem $13\mathrm{.}6($Intermediate$)$: Write and test a function M$-$file nat add in for the

element$-$by$-$element addition of matrices A and a using Equation $13\mathrm{.}3.$ An appro$-$

priate function declaration is

$[$ matrixaum $]=$ matadd $($ A$,$ B $)$

After your M$-$file function has checked that matrices A and $B$ have compatible sizns.

Equation $13\mathrm{.}3$ should be evaluated inside a set of two nested for loops.

Write a test program to allocate and initialize matrices A and $B,$ and compute

their sum using the mat ada function and MATLAB's built$-$in library for matrir

addition. What is the relative speed of these two approaches?