using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var data = new List<List<(int, int)>>() {

            new List<(int, int)> { (0, 1), (2, 4), (3, 8) },

            new List<(int, int)> { (2, 0), (3, 3), (4, 1), (6, 5)}

        };

        // a is accumulator, c is current item

        var result = data.Select(lst =>  

           lst.Aggregate( (a, c) => (a.Item1 + c.Item1, a.Item2 + c.Item2) ) 

        );

        foreach(var item in result)

        {

            Console.WriteLine($"({item.Item1}, {item.Item2})");

        }

    }

}