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#include <cstdlib>
#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;
double calculate_full_repayment(double p, int y, double i);
double calculate_monthly_repayment(double p, int y, double i);
void print_repayment(bool full_repayment, double p, int y, double i);
int main()
{
int base_loan_years = 5;
double base_loan_amount = 0;
double base_loan_interest = 0.0;
cout << "Welcome to Repayment of a Loan!\n\n";
cout << "Please enter the dollar amount of your loan: ";
cin >> base_loan_amount;
cout << "Please enter the starting interest rate (e.g. 4.75 for 4.75%): ";
cin >> base_loan_interest;
cout << "\n\n";
cout << fixed << setprecision(2) << "\t\t\t\tLoan of " << base_loan_amount << " dollars";
cout << "\n\n";
cout << "\t\t\t\t Monthly Repayment";
cout << "\n\n";
cout << "\t\t\t\t Interest Rates";
cout << "\n";
// Print header for years and rates.
cout << "\tYears";
for (int i = 0; i < 5; i++)
{
double interest = (base_loan_interest + (0.5 * i));
cout << fixed << setprecision(2) << "\t" << setw(11) << right << interest << "%";
}
cout << "\n";
// Print monthly payment.
print_repayment(false, base_loan_amount, base_loan_years, base_loan_interest);
cout << "\n";
cout << "\t\t\t\tTotal Amount Paid in Repayments";
cout << "\n";
// Print full re-payment amount.
print_repayment(true, base_loan_amount, base_loan_years, base_loan_interest);
return 0;
}
void print_repayment(bool full_repayment, double p, int y, double i)
{
// P = Base Loan Amount
// I = Full Interest
// Y = Base Year
for (int row = 0; row < 6; row++)
{
for (int col = 0; col < 6; col++)
{
int years = y + (5 * row);
if (col > 0)
{
double full_interest = (i + (0.5 * (col - 1)));
double repayment;
if (full_repayment)
{
repayment = calculate_full_repayment(p, years, full_interest / 100);
}
else
{
repayment = calculate_monthly_repayment(p, years, full_interest / 100);
}
cout << fixed << setprecision(2) << "\t$" << setw(11) << right << repayment;
}
else
{
cout << "\t" << years;
}
}
cout << "\n";
}
}
double calculate_full_repayment(double p, int y, double i)
{
// P = Principal
// I = Interest
// Y = Years
// R = Monthly Repayment
// F = Full Repayment Amount
// 12 monthly repayments * number of years paid across
// F = R * 12 * Y
double f = calculate_monthly_repayment(p, y, i) * 12 * y;
return f;
}
double calculate_monthly_repayment(double p, int y, double i)
{
// P = principal
// I = Interest
// Y = Years
// R = Monthly Repayment
// R = (P * (i / 12)) * (((1 + (i / 12)) ^ (12 * y)) / (((1 + (i / 12)) ^ (12 * y)) - 1))
// Calculate (1 + (i / 12)) ^ (12 * y) since it's used twice.
double partial_work = pow((1 + (i / 12)), (12 * y));
double r = (p * (i / 12)) * (partial_work / (partial_work - 1));
return r;
}
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