main.cpp 나 Item.cpp 를 실행해보면 둘 다 undefined reference 에러가 뜨는데 초보라 여기서 더 이상 고칠수가 없네요. 무엇이 문제인지 알려주시면 정말 감사하겠습니다.

main.cpp
---------------
#include <iostream>
#include "Item.h"

int main(){
Item item1{ "Potato Chips", 1.78 };
Item item2{ "Doritos", 1.99, 2 };

std::cout << item1.get_name() << '\n';

std::cout << "Original " << item2.get_name()  << '\n';;
std::cout << "Price:   " << item2.get_price() << '\n';
item2.set_price(2.49);
std::cout << "Updated  " << item2.get_name()  << '\n';;
std::cout << "Price:   " << item2.get_price() << '\n';
    return 0;
}


Item.h
-----------
#ifndef ITEM_H
#define ITEM_H
#include <string>

class Item {
  public:
    Item(std::string name, double price, int quantity=1);
    std::string get_name() const;
    double get_price() const;
    int get_quantity() const;

    void set_price(double new_price);
    void set_quantity(double new_quanity);
  private:
    std::string name;
    double      price;
    int         quantity;
};

#endif



Item.cpp
--------------
#include "Item.h"
#include <iostream>
using std::string;

Item::Item(std::string name, double price, int quantity){
    this->name      = name;
    this->price     = price;
    this->quantity  = quantity;}

    string Item::get_name() const{
    return name;
}

double Item::get_price() const{
    return price;
}

int Item::get_quantity() const{
    return quantity;
}

void Item::set_price(double new_price){
    price = new_price;
}

void Item::set_quantity(double new_quanity){
    price = new_quanity;
}