How to write an electricity bill in c program(9'th class)

#include <iostream.h>
#include <conio.h>
int main()
{
clrscr();
long int units,charge=0;
float total;
const int rent=25;
cout << "Enter the number of units used : ";
cin>>units;
if(units>200)
charge=(units-200)*20+150*40+50*60;
else if(units>50)
charge=(units-50)*40+50*60;
else
charge=units*60;
total=0.01*charge+rent;
cout << "You have used " << units << " units." << endl;
cout << "Your total telephone bill is $" << total;
getch();
return 0;


Please accept the solution. Thanks, Lucy
}
This program takes in the number of units used ('units') as a screen input from the user.
It then calculates the total telephone bill for the customer on the following basis :
A compulsory fee of $25, plus
60 cents per unit for the first 50 units,
40 cents per unit for the next 150 units,
20 cents per unit for anything above 200 units.
It then outputs the bill using the 'cout' command.