using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var transactionDetails = new List<TransactionDetail>

        {

            new TransactionDetail()

            {

                AccountNumber = "0001123456",

                TransactionNumber = 1,

                Amount = 1000

            },          

            new TransactionDetail()

            {

                AccountNumber = "WRAP987654",

                TransactionNumber = 10,

                Amount = 30000

            },          

            new TransactionDetail()

            {

                AccountNumber = "0001123456",

                TransactionNumber = 20,

                Amount = 200

            },

        };

        List<Account> accounts = ExtractAccounts(transactionDetails);

    }

    public static List<Account> ExtractAccounts(List<TransactionDetail> transactionDetails)

    {

        // Code here

        throw new NotImplementedException(); 

    }

​

}

​

public class TransactionDetail

{

    public int TransactionNumber { get; set; }

    public string AccountNumber { get; set; }

    public double Amount { get; set; }

}

​

public class Account

{

    public string AccountNumber { get; set; }

    public List<Transaction> Transactions { get; set; }

}

​

public class Transaction

{

    public int TransactionNumber { get; set; }

    public double Amount { get; set; }

}