access modifier

This is an example for Inheritance and it is using the get() and set() method. Employee class has two data field empNum & empSal. I wish to convert this program to automatic property. During the conversation empNum's access modifier private will become public. But empSal is access modifier is protected. I wish to know its change during conversation.

//p243
//Declaring empSal as protected and accessing it with CommissionEmployee

using System;
public class DemoEmployees
{
public static void Main()
{
Employee clerk = new Employee();
CommissionEmployee salesperson = new CommissionEmployee();

clerk.SetEmpNum(5612);
clerk.SetEmpSal(425.00);

salesperson.SetEmpNum(3198);
salesperson.SetRate(0.07);

Console.WriteLine("\nCleark #{0} makes {1} per week", clerk.GetEmpNum(), clerk.GetEmpSal().ToString("C2"));

Console.WriteLine("\nSalesperson #{0} makes {1} per week", salesperson.GetEmpNum(), salesperson.GetEmpSal().ToString("C2"));

Console.WriteLine("...plus {0} percent commission on all sales", salesperson.GetRate());
}
}
internal class Employee
{
private int empNum;
protected double empSal;//empSal is protected, not private

public int GetEmpNum()
{
return empNum;
}
public void SetEmpNum(int num)
{
empNum = num;
}

public double GetEmpSal()
{
return empSal;
}
public void SetEmpSal(double sal)
{
empSal = sal;
}
}
class CommissionEmployee : Employee
{
private double commissionRate;

public double GetRate()
{
return commissionRate;
}
public void SetRate(double rate)
{
commissionRate = rate;
empSal = 0;//If empSal was private, this would be illegal
}
}
/*

Cleark #5612 makes $425.00 per week

Salesperson #3198 makes $0.00 per week
...plus 0.07 percent commission on all sales
*/