Simple c++ coding to find out monthly telephone bill using while loop id if else statement.

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There must be the word "iostream" in <> after include in first line.

#include
#include<conio.h>
using namespace std;
int main()
{
int si,calls;
float bill;
while(true)
{
cout<<"enter the serial number"<<endl;
cin>>si;
if(si==0)
{
break;
}
cout<<"enter the number of calls"<<endl;
cin>>calls;
if(calls<=100)
{
bill=200;
}

    else if(calls>100 && calls<=150)
    {
        calls=calls-100;
        bill=200+(calls*0.60);
    }
     else if(calls>150 && calls<=200)
    {
        calls=calls-150;
        bill=200+(50*0.60)+(calls*0.50);
    }
     else
    {
        calls=calls-200;
        bill=200+(50*0.60)+(50*0.50)+(calls*0.40);
    }
    cout<<"the total bills tk ="<<bill<<endl;
}
getch();

}