using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var parents = new [] 

        {

            new Parent { TransactionId = 1, PayAmount = 1000},

                new Parent { TransactionId = 2, PayAmount = 3000},

                new Parent { TransactionId = 3, PayAmount = 5000},

                new Parent { TransactionId = 4, PayAmount = 6000}

        };

        var children = new []

        {

                new Child { Id = 1, TransactionId = 1, DepositAmount=600},

                new Child { Id = 2, TransactionId = 1, DepositAmount=400},

                new Child { Id = 3, TransactionId = 2, DepositAmount=1000},

                new Child { Id = 4, TransactionId = 2, DepositAmount=1000},

                new Child { Id = 5, TransactionId = 2, DepositAmount=1000},

                new Child { Id = 6, TransactionId = 3, DepositAmount=2000}

        };

        var dueParents = parents.Where(parent => parent.PayAmount > children.Where(child => child.TransactionId == parent.TransactionId).Sum(child => child.DepositAmount));

        foreach (var due in dueParents)

        {

            Console.WriteLine(due.TransactionId);

        }

    }

    public class Parent

    {

        public int TransactionId{get;set;}

        public decimal? PayAmount{get;set;}

    }

        public class Child 

        {

            public int Id {get;set;}

            public int TransactionId {get;set;}

            public decimal? DepositAmount {get;set;}

        }

}