복사생성자, 연산자 오버로딩 부분 이상하게 안됩니다

#include<iostream>
 
using namespace std;
 
class TwoD
{
private:
	double** arr;
	double MaxRows;
	double MaxCols;
public:
	TwoD()// 가로세로 10 짜리 배열 생성
		:MaxRows(10), MaxCols(10)
	{
		arr = new double* [MaxRows];
		for (int i = 0; i < MaxRows; i++)
		{
			arr[i] = new double[MaxCols];
		}
	}
	TwoD(double a, double b)
		:MaxRows(b), MaxCols(a)
	{
		arr = new double* [MaxRows];
		for (int i = 0; i < MaxRows; i++)
		{
			arr[i] = new double[MaxCols];
		}
	}
	int getcols()
	{
		return MaxCols;
	}
	int getrows()
	{
		return MaxRows;
	}
	double operator[](int i)
	{
		return *(arr[i]);
	}
	void set(int col, int row, int value)
	{
		arr[col][row] = value;
	}
	double returnvalue(int col, int row)
	{
		return arr[col][row];
	}
	const TwoD& operator=(const TwoD& r)// c.=(a);
	{
 
		for (int i = 0; i < MaxRows; i++)
		{
			delete[] arr[i];
		}
		delete[] arr;
 
		MaxRows = r.MaxRows;
		MaxCols = r.MaxCols;
 
		arr = new double* [MaxRows];
		for (int i = 0; i < MaxRows; i++)
		{
			arr[i] = new double[MaxCols];
		}
 
		for (int i = 0; i < MaxRows; i++)
		{
			for (int j = 0; j < MaxCols; j++)
			{
				arr[i][j] = r.arr[i][j];
			}
		}
		return *this;
	}
	friend TwoD& operator+(const TwoD& a, const TwoD& b);
	void print()
	{
		for (int i = 0; i < MaxRows; i++)
		{
			for (int j = 0; j < MaxCols; j++)
			{
				cout << arr[i][j] << " ";
			}
			cout << "\n";
		}
	}
 
	~TwoD()
	{
		for (int i = 0; i < MaxRows; i++)
		{
			delete[] arr[i];
		}
		delete[] arr;
	}
};
int main()
{
	TwoD a(1, 1);
	TwoD b(1, 1);
	double s;
	cout << "a 배열 입력\n";
	for (int i = 0; i < a.getrows(); i++)
	{
		for (int j = 0; j < a.getcols(); j++)
		{
			cin >> s;
			a.set(i, j, s);
		}
	}
	cout << "b 배열 입력\n";
	for (int i = 0; i < b.getrows(); i++)
	{
		for (int j = 0; j <b.getcols(); j++)
		{
			cin >> s;
			b.set(i, j, s);
		}
	}
	TwoD c(1, 1);
	c = a;
	c.print();
	c = a + b;
	c.print();
	return 0;
}
TwoD& operator+(const TwoD& a, const TwoD& b)
{
	TwoD r(a.MaxRows, a.MaxCols);
 
	for (int i = 0; i < a.MaxRows; i++)
	{
		for (int j = 0; j < a.MaxCols; j++)
		{
			r.arr[i][j] = a.arr[i][j] + b.arr[i][j];
		}
	}
	return r;
}