Scalar Vector Multiplication using class Template

#include <iostream>
#include <cstdlib>

using namespace std;

template <class T, int s = 3>
class Vector{
    T *arr;
    int size;
    public:
        Vector();
        Vector(int);
        Vector(const Vector<T, s>&);
        ~Vector();
        Vector<T, s> operator *(T);
        // Produces ERROR
        //friend Vector<T, s> operator *(T, const Vector<T ,s>&);
        Vector<T, s>& operator =(const Vector<T,s>&);
        void display();
        void input();
};

template <class T, int s>
Vector<T, s>::Vector(){
    size = s;
    arr = new T[size];
}

template <class T, int s>
Vector<T, s>& Vector<T, s>::operator =(const Vector<T,s> &obj){
    for(int i = 0; i < size; i++){
        arr[i] = obj.arr[i];
    }
    return *this;
}

template <class T, int s>
Vector<T, s>::Vector(int size){
    arr = new T[Vector<T>::size = size];
}

template <class T, int s>
Vector<T, s>::Vector(const Vector<T, s> &obj){
    arr = new T[size = obj.size];
    for(int i = 0; i < size; i++){
        arr[i] = obj.arr[i];
    }
}

template <class T, int s>
Vector<T, s>::~Vector(){
    delete[] arr;
}

template <class T, int s>
void Vector<T, s>::display(){
    for(int i = 0; i < size; i++){
        cout << arr[i] << " ";
    }
    cout << endl;
}

template <class T, int s>
void Vector<T, s>::input(){
    for(int i = 0; i < size; i++){
        cout << "arr[" << i << "] = ";
        cin >> arr[i];
    }
}

template <class T, int s>
Vector<T, s> Vector<T, s>::operator *(T multiplier){
    Vector<T> temp(size);
    for(int i = 0; i < size; i++){
        temp.arr[i] = multiplier * arr[i];
    }
    return temp;
}

// Produces ERROR
/*
template <class T, int s>
Vector<T, s> Vector<T, s>::operator *(T multiplier, const Vector<T, s> &obj){
    Vector<T> temp(obj.size);
    for(int i = 0; i < size; i++){
        temp.arr[i] = multiplier * obj.arr[i];
    }
    return temp;
}
*/

int main() {
    int size;
    cout << "Enter the length of the vector: ";
    cin >> size;
    Vector<int> obj(size);
    cout << "Input values" << endl;
    obj.input();
    int multiplier;
    cout << "Enter the multiplier: ";
    cin >> multiplier;
    cout << "Before multiplying" << endl;
    obj.display();
    obj = obj * multiplier;
    cout << "After multiplying" << endl;
    obj.display();
    return 0;
}