Методы синхронизации C# и многопоточность

So I started this question, I believe i have synchronized the methods correctly, need some insight on whats wrong and what should be done. I have to modify ths class Purse so that the method AddCoin is synchronized and implement a synchronized RemoveCoin method with a Coin argument, I believe that is done just fine. Where im really having trouble is implementing thread that adds pennies, another thread that adds quarters, and another thread that removes and prints randomly selected coins, pennies, quarters, any one. Then finally synchronize the threads to wait for each other when necessary. Here is what I have so far:

Purse.cs

using System;
using System.Collections;
using System.Threading;

namespace TestingProject
{
    /// <summary>
    /// A purse holds a collection of coins.
    /// </summary>
public class Purse
{
    ///  Constructs an empty purse.
    public Purse()
    {
        coins = new ArrayList();

    }

    ///   Add a coin to the purse.
    ///   @param aCoin the coin to add
    public void Add(Coin aCoin)
    {
        Monitor.Enter(coins);
        coins.Add(aCoin);
        
        Monitor.Exit(coins);
    }
    public void RemoveCoin(Coin aCoin)
    {
        Monitor.Enter(coins);
        coins.Remove(aCoin);
        
        Monitor.Exit(coins);
    }
    

    ///  Get the total value of the coins in the purse.
    ///  @return the sum of all coin values
    public double GetTotal()
    {
        double total = 0;
        for (int i = 0; i < coins.Count; i++)
        {
            Coin aCoin = (Coin)coins[i];
            total = total + aCoin.GetValue();
        }
        return total;
    }

    private ArrayList coins;
}



}
Coin.cs

using System;
using System.Collections;

namespace TestingProject
{
    /// <summary>
    /// A coin with a monetary value.
    /// </summary>
public class Coin   {

    /// Constructs a coin.
    /// @param aValue the monetary value of the coin
    /// @param aName the name of the coin
    public Coin(double aValue, String aName) 
    { 
        value = aValue; 
        name = aName;
    }

    public Coin()
    {
    }

    /// Gets the coin value.
    /// @return the value
    public double GetValue()    
    {
        return value;
    }

    /// Gets the coin name.
    /// @return the name
    public String GetName() 
    {
        return name;
    }
    
    public override bool Equals(Object otherObject)
    {
        Coin other = (Coin)otherObject;
        return name==other.name
            && value == other.value;
    }

    // C# requirement: 
    // since we override Equals, MUST also override GetHashCode ( !! )
    public override int GetHashCode()
    {
        return base.GetHashCode ();
    }

    private double value;
    private string name;
}
}
pursetest.cs

using System;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.VisualBasic;


namespace TestingProject
{


class PurseTest
{
    public static void Main(string[] args)
    {
        

        // Random object used by each thread
        Random random = new Random();

        
        Purse purse =new Purse();

        Coin coin = new Coin();

        // output column heads and initial buffer state
        Console.WriteLine("{0,-35}{1,-9}{2}\n",
           "Operation", "Buffer", "Occupied Count");


        
        Thread purseThread =
           new Thread(new ThreadStart(purse.Add))
           {
               Name = "Purse"
           };

        Thread coinThread =
           new Thread(new ThreadStart(coin.GetValue));
        coinThread.Name = "coin";

        // start each thread
        purseThread.Start();
        coinThread.Start();

    }
}
}