Async quiz: How many threads are used? What does it print?

async.cs

using System;
using System.Runtime.CompilerServices;
using System.Threading.Tasks;

// The more evil version. :)

class Program
{
    static void Main(string[] args)
    {
        var startWorkTcs = new TaskCompletionSource<object>();
        var workDoneTcs = new TaskCompletionSource<object>();

        var workTask = SomethingAsync(startWorkTcs, workDoneTcs);
        var waiter = DoWait(workDoneTcs, workTask);

        // Pre-work output.
        Console.WriteLine("Hello");

        // Start the work.
        startWorkTcs.TrySetResult(null);

        // Post-work output.
        Console.WriteLine("World");

        // Wait for the work to complete.
        waiter.Wait();
    }

    static async Task DoWait(TaskCompletionSource<object> workDoneTcs, Task workTask)
    {
        // Asynchronously wait for the work to report that it's done.
        await workDoneTcs.Task;

        // Now wait for the actual work task to complete.
        workTask.Wait();
    }

    private static async Task SomethingAsync(TaskCompletionSource<object> startWorkTcs, TaskCompletionSource<object> workDoneTcs)
    {
        // Asynchronously wait for the signal to start work.
        await startWorkTcs.Task;

        // Do the work.
        Console.WriteLine("Beautiful");

        // Notify caller that the work is done.
        workDoneTcs.TrySetResult(null);
    }
}