Usage of Private Protected in C#

Private_Protected.cs

/* =========================================================================
*  First Assembly (ProjectOne.csproj)
* =========================================================================*/

namespace ProjectOne
{
    public class Sample
    {
        public void SomeMethod()
        {
            // Allowed from same class
            var result = Calculate(3, 5);
        }

        private protected int Calculate(int x, int y)
        {
            return x + y;
        }
    }

    public class DerivedSample : Sample
    {
        public void SomeOtherMethod()
        {
            // Allowed, as Derived class is in same assembly
            var result = Calculate(4, 6);
        }
    }

    public class AnotherSample
    {
        public void SomeOtherMethod()
        {
            Sample s = new Sample();

            // Not Allowed, even if declaring class is in same assembly
            // var result = s.Calculate(4, 6);
        }
    }
}


/* =========================================================================
*  Second Assembly (ProjectTwo.csproj)
* =========================================================================*/
namespace ProjectTwo
{
    using ProjectOne;

    public class DerivedSampleTwo: Sample
    {
        public void SomeOtherMethod()
        {
            // Not Allowed, if derived class is in any other assembly
            // var result = Calculate(9, 8);
        }
    }

    public class RandomClass
    {
        public void SomeOtherMethod()
        {
            Sample s = new Sample();

            // Not Allowed, from any other assembly
            s.Calculate(10, 10);
        }
    }
}