For C$++$

A mobile phone service provider has three different data plans for its customers:

Plan A $-$ For $$39\mathrm{.}99$ per month, $2$ gigabytes are provided. Additional usage costs $$8\mathrm{.}00$ per gigabyte.

Plan B $-$ For $$59\mathrm{.}99$ per month, $8$ gigabytes are provided. Additional usage cost $$8\mathrm{.}00$ per gigabyte.

Plan C $-$ For $$79\mathrm{.}99$ per month, unlimited data is provided.

Write a program that calculates a customer's monthly bill. It should input the customer name, which plan was purchased, and how many gigabytes were used. It should then create a bill that includes the input information and the total amount due. It should also display how much money plan A customers would save if they purchased plan B or C$,$ and how much money plan B customers would save if they purchased plan C$.$ If there would be no savings, no message should be printed. Wherever possible, use named constants instead of numbers, this part is important.

This is what I have and it's not doing the savings correctly. What am I missing?

#include

#include

using namespace std;

$//$ Constants

const double plan$\_$A$\_$price $=39\mathrm{.}99$;

const int plan$\_$A$\_$included $=2$;

const double plan$\_$A$\_$extra $=8\mathrm{.}00$;

const double plan$\_$B$\_$price $=59\mathrm{.}99$;

const int plan$\_$B$\_$included $=8$;

const double plan$\_$B$\_$extra $=8\mathrm{.}00$;

const double plan$\_$C$\_$price $=79\mathrm{.}99$;

$//$ To calculate total bill for each plan

void calculateBill$($char plan, double usedData$)\{$

double totalCost, savingsB, savingsC;

switch $($plan$)\{$

case $\text{'}$A$\text{'}$:

totalCost $=$ plan$\_$A$\_$price;

if $($usedData $>$ plan$\_$A$\_$included$)\{$

totalCost $+=($usedData $-$ plan$\_$A$\_$included$)*$ plan$\_$A$\_$extra;

$\}$

savingsB $=($totalCost $<$ plan$\_$B$\_$price$)?$ plan$\_$B$\_$price $-$ totalCost : $0$;

savingsC $=($totalCost $<$ plan$\_$C$\_$price$)?$ plan$\_$C$\_$price $-$ totalCost : $0$;

break;

case $\text{'}$B$\text{'}$:

totalCost $=$ plan$\_$B$\_$price;

if $($usedData $>$ plan$\_$B$\_$included$)\{$

totalCost $+=($usedData $-$ plan$\_$B$\_$included$)*$ plan$\_$B$\_$extra;

$\}$

savingsB $=0$;

savingsC $=($totalCost $<$ plan$\_$C$\_$price$)?$ plan$\_$C$\_$price $-$ totalCost : $0$;

break;

case $\text{'}$C$\text{'}$:

totalCost $=$ plan$\_$C$\_$price;

savingsB $=0$;

savingsC $=0$;

break;

default:

cout $<<$ "Invalid plan choice." $<<$ endl;

return;

$\}$

$//$ To display the bill

cout $<<$ fixed $<<$ setprecision$(2)$;

cout $<<$ "Total Amount Due: $$"<<$ totalCost $<<$ endl;

$//$ To display the savings for Plan A and Plan B customers

if $($plan $==\text{'}$A$\text{'})\{$

if $($totalCost $<$ plan$\_$B$\_$price && savingsB $>0)\{$

cout $<<$ "Savings if you had purchased Plan B: $$"<<$ savingsB $<<$ endl;

$\}$

if $($totalCost $<$ plan$\_$C$\_$price && savingsC $>0)\{$

cout $<<$ "Savings if you had purchased Plan C: $$"<<$ savingsC $<<$ endl;

$\}$

$\}$ else if $($plan $==\text{'}$B$\text{'})\{$

if $($totalCost $<$ plan$\_$C$\_$price && savingsC $>0)\{$

cout $<<$ "Savings if you had purchased Plan C: $$"<<$ savingsC $<<$ endl;

$\}$

$\}$

$\}$

int main$()\{$

string customerName;

char planPurchased;

double gigabytesUsed;

cout $<<$ "Enter customer name: $"$;

cin $>>$ customerName;

cout $<<$ "Enter plan purchased $($A$,$ B$,$ or C$)$: $"$;

cin $>>$ planPurchased;

cout $<<$ "Enter the number of gigabytes used: $"$;

cin $>>$ gigabytesUsed;

cout $<<"------------------"<<$ endl;

cout $<<$ "Your Phone Bill" $<<$ endl;

cout $<<$ "Customer Name: $"<<$ customerName $<<$ endl;

cout $<<$ "Plan Purchased: $"<<$ planPurchased $<<$ endl;

cout $<<$ "Gigabytes Used: $"<<$ gigabytesUsed $<<$ endl;

calculateBill$($toupper$($planPurchased$),$ gigabytesUsed$)$;

return $0$;

$\}$