Solution: Invoice Generator

#include <iostream>
// Overload 1: Calculates price for discrete items (quantity is int)
double calculatePrice(double pricePerUnit, int quantity) {
    return pricePerUnit * quantity;
}
// Overload 2: Calculates price for weighted items (weight is double)
double calculatePrice(double pricePerKg, double weight) {
    return pricePerKg * weight;
}
// Updates total by reference. Uses a default taxRate of 5% if not provided.
void addToTotal(double& total, double itemCost, double taxRate = 0.05) {
    double taxAmount = itemCost * taxRate;
    double finalAmount = itemCost + taxAmount;
    total += finalAmount;
    
    std::cout << "Added item: $" << itemCost 
              << " + Tax: $" << taxAmount 
              << " = $" << finalAmount << "\n";
}
int main() {
    double invoiceTotal = 0.0;
    // 1. Buy 3 Books at $10.00 each
    // Compiler selects Overload 1 because 3 is an integer
    double booksCost = calculatePrice(10.00, 3);
    
    // Updates invoiceTotal using the default 5% tax
    addToTotal(invoiceTotal, booksCost);
    // 2. Buy 2.5 kg of Fruit at $4.00 per kg
    // Compiler selects Overload 2 because 2.5 is a double
    double fruitCost = calculatePrice(4.00, 2.5);
    
    // Updates invoiceTotal with 0% tax (overriding the default)
    addToTotal(invoiceTotal, fruitCost, 0.0);
    std::cout << "Final Invoice Total: $" << invoiceTotal << "\n";
    return 0;
}