using namespace std;

$/*$

NumberList::NumberList$()$

$\{$

$\}$

NumberList::NumberList$($int l$,$ double n$)$

$\{$

$\}$

NumberList::NumberList$($int l$,$ const double a$[])$

$\{$

$\}$

NumberList::NumberList$($const NumberList & nl$)$

$\{$

$\}$

void NumberList::print$()$

$\{$

$\}$

int NumberList::getLength$()$

$\{$

$\}$

double NumberList::sum$()$

$\{$

$\}$

double NumberList::ave$()$

$\{$

$\}$

double NumberList::max$()$

$\{$

$\}$

double NumberList::min$()$

$\{$

$\}$

bool NumberList::isIn$($double n$)$

$\{$

$\}$

bool NumberList::push$($double value$)$

$\{$

$\}$

bool NumberList::pop$()$

$\{$

$\}$

void NumberList::read$($istream & inStream$)$

$\{$

if$($&inStream $==$ &cin$)$

$\{$

$\}$

else

$\{$

$//$file structure: first line contains the number of numbers in the list

$//$remaining lines contain the numbers each separated by a whitespace

$\}$

$\}$

bool NumberList::insert$($double number, int position$)$

$\{$

$\}$

$//$SELECTION SORT algorithm

void NumberList::sort$($char type$)$

$\{$

$\}$

bool NumberList::operator$==($const NumberList& rhs$)$

$\{$

$\}$

NumberList& NumberList::operator$=($const NumberList& rhs$)$

$\{$

$//$avoid self$-$assignment, only do assignment if RHS is a different object from this

if$($this $!=$ &rhs$)$

$\{$

$\}$

return $*$this;

$\}$

NumberList& NumberList::operator$+=($const double& number$)$

$\{$

if$($length $==100)$

cout $<<$ "Unable to perform $+=,$ list is filled to capacity

$"$;

else

$\{$

$\}$

return $*$this;

$\}$

NumberList& NumberList::operator$+=($const NumberList& rhs$)$

$\{$

if$($length $==100)$

cout $<<$ "Unable to perform $+=,$ list is filled to capacity

$"$;

else if$($length $+$ rhs$.$length $>100)$

cout $<<$ "Unable to perform $+=,$ list would be over capacity

$"$;

else

$\{$

$\}$

return $*$this;

$\}$

$//**************************************$

$//$FOR $10\%$ EXTRA CREDIT ON THIS PROJECT GRADE, OVERLOAD THE FOLLOWING OPERATORS

$//$AS NON$-$MEMBER FUNCTIONS

ostream& operator$<<($ostream& out, const NumberList& nl$)$

$\{$

$\}$

const NumberList operator$+($NumberList& lhs$,$ const double& number$)$

$\{$

$\}$

const NumberList operator$+($NumberList& lhs$,$ const NumberList& rhs$)$

$\{$

$\}$

$*/$

Create a testNL.cpp with invoice.txt of

$6$

$123456$

#include "NumberList.h$"$#include $$#include $$using namespace std;$$int main$()\{\}$