I am a beginner c++ student with an assignment to create a car loan calculator. I am having trouble with the calculations of the monthly payment, which I assume is because the operands are of different types in the equation? I am also not able to produce the results for the number of payments, total amount owed and total interest paid. If someone could look over my code, I would appreciate any input to help get my program working correctly!

//Date: 2/15/2011

// Programmer: Lindsay Lewis

// Description: This program computes the monthly payment for a car loan

#include <iostream>

#include <iomanip>

#include <cmath>

using namespace std;

int main()

{

// This step requires the user to input the type of vehicle

string car_type;

cout << "Enter the type of vehicle: ";

getline (cin,car_type);

// This step requires the user to input the purchase price of the car

double purchase_price;

cout << "Enter the purchase price of the car: ";

cin >> purchase_price;

// This step requires the user to input the amount of the down payment

double down_payment;

cout << "Enter the amount of your down payment: ";

cin >> down_payment;

// This step requires the user to input the number of years to pay off the car

int years;

cout << "Enter the number of years to pay off the car: ";

cin >> years;

// This step requires the user to input the interest rate

float interest_rate;

cout << "Enter the annual interest rate:";

cin >> interest_rate;

// This step calcuates the interest rate

double interest;

interest = interest_rate / 100;

// This step defines the value for the amount to be financed

double amount_financed;

amount_financed = purchase_price - down_payment ;

// This step defines the number of payments per year

int payments_year;

payments_year = 12;

// This step calculates the monthly payment

double monthly_payment;

monthly_payment = (amount_financed * (interest / payments_year)) /(1 - pow(1+\

interest / payments_year),(-payments_year * years));

// This step calculates the number of payments

double number_payments;

number_payments = years - monthly_payment;

// This step calculates the total amount owed

double total_amount_owed;

total_amount_owed = number_payments * monthly_payment;

// This step calculates the total interest paid

double total_interest_paid;

total_interest_paid = monthly_payment * number_payments - amount_financed;

// This step calculates the number of payments

double number_payments;

number_payments = years - monthly_payment;

// This step calculates the total amount owed

double total_amount_owed;

total_amount_owed = number_payments * monthly_payment;

// This step calculates the total interest paid

double total_interest_paid;

total_interest_paid = monthly_payment * number_payments - amount_financed;

cout << left;

cout << setw(40) << "Monthly Car Loan Payment Calculation" << endl;

cout << setw(40) << "========================================" << endl;

cout << setw(40) << "Type of Vehicle:" << car_type << endl;

cout << setw(40) << "Purchase Price:" << purchase_price << endl;

cout << setw(40) << "Down Payment:" << down_payment << endl;

cout << setw(40) << "Amount Financed:" << amount_financed << endl;

cout << setw(40) << "Length of Loan:" << years << endl;

cout << setw(40) << "Annual Interest Rate:" << interest_rate << endl;

cout << setw(40) << "Monthly Payment:" << monthly_payment << endl;

cout << setw(40) << "Number of Payments:" << number_payments << endl;

cout << setw(40) << "Total Amount Owed:" << total_amount_owed << endl;

cout << setw(40) << "Total Interest Paid:" << total_interest_paid << endl;

}