how to pass function return from switch

How to do i fix this code im not good at using function, im trying to pass a statement from switch to my double passengersR i always come out with a error

this output:
Name passenger:
Enter number passenger:
Choose from A to D
if choose A
Total Regular Passenger: 6.19624e-312

did i do something wrong im not really good at function and im trying to learn how to pass switch to void function

Code:

---

#include<conio.h>
#include <iostream>
#include <Iomanip>
#include <string>

using namespace std;

double passengersR ()
{
     
double m;
int num;

m=120*num;
return m;

}

int main()
{
    double passengersR ();
    double m;
    char x ;
    string Name;
    float tickPrice;
    int  num;
    string morePassengers,name;
   
    cout<<"Enter Passenger Name:";
    cin>> Name;
    cout<<"Enter Number of passenger ";
    cin >> num;
    cout<<" A.Regular B.Student  C.Senior D.Children ";
    cin>>x ;
       
    cout << endl << endl;
    cout << x << endl ;
   
   
    switch (x)
    {
    case 'a':
    case 'A':     
    cout<<"Total Regular Passenger:" << m << endl;     
    break;
    }
   
   
   
   
    getch();

}

---

Code:

---

    double passengersR (); // this is a declaration of the function passengersR
    double m; // Here a variable m is declared, its value is undefined

---

guess that is not what you want

Code:

---

    double m = passengersR (); // Here a variable m is declared, it is initialized with the return value of the call to passengersR

---

But then you still have a problem

Code:

---

double passengersR ()
{
     
double m;
int num;  // the value of num is undefined could be any value

m=120*num; // if you multiply an undefined value by 120 still gives you an undefined value
return m;

}

---

Kurt

cout<<"Enter Number of passenger "; cin >> num;

Code:

---

m=120*num;

---

The num here is for the how many the passenger. for example 120 x 12 = 1440

i just don't know how to call my function and display or return value on my switch case

Total Regular Passenger: 6.19624e-312 this always my problem how do i fix this problem?

I understand but the num in passengersR () is a different num from the one in main.
Guess you have to pass it as a parameter to the function
e.g.

Code:

---

double passengersR ( int num ) { 
    double m;
    m=120*num;
    return m;
}

---

and call it like this

Code:

---

cout<<"Enter Number of passenger "; cin >> num;
double m = passengersR (num);

---

Kurt

Thanks Alot Its my first time using function when trying to call from a switch you help me alot