What am i doing wrong with the math?

Question

private void btnDisplay_Click(object sender, EventArgs e)

    {
        string EmploymentStatus = Convert.ToString(txtES.Text).ToLower();
        string UnionStatus = Convert.ToString(txtMS.Text).ToLower();
        double TotalSales = Convert.ToDouble(txtSales.Text) * 9.25;
        double Years = Convert.ToDouble(txtYears.Text);         
        double uniondues;
        double FICA = 0;
        double bonus = 0;
        double WPay = 0;
        double TotalComission = 0;

        if (EmploymentStatus == "full")
        {                 
            WPay = 800.00;
        }
        else if (EmploymentStatus == "part")
        {
            WPay = 200.00;
        }
        else
        {
            MessageBox.Show("Error, please enter either FULL or PART");
        }

            if (UnionStatus == "member")
            {
                uniondues = 5.25;
                WPay = WPay - uniondues;
            }
            else if (UnionStatus == "non-member")
            {
                uniondues = 0;
            }
            else
            {
                MessageBox.Show("Error, please enter either MEMBER or NON-MEMBER");
            }
            if ((EmploymentStatus == "full") && (TotalSales > 640))
            {
                bonus = TotalSales * .05;

            }
            else if (EmploymentStatus == "part")
            {
                bonus = 0;
            }
            if (Years >= 10)
            {
                TotalComission = TotalSales * .10;

            }
            else if (Years < 10)
            {
                TotalComission = TotalSales * .05;

            }
            else
            {
                MessageBox.Show("Error, please enter a valid number");
            }


            FICA = WPay * .16;
            WPay = WPay - FICA;


        lblqWPay.Text = "The weekly pay for the employee is: " + (WPay.ToString("C"));
        lblqTS.Text = "The total sales for this employee is: " + (TotalSales.ToString("C"));
        lblqCom.Text = "The comission for this employee is: " + (TotalComission.ToString("C"));
        lblqBonus.Text = "The bonus for this employee is: " + (bonus.ToString("C"));

When i enter the employment status as "FULL" and union status as "MEMBER", with the quantity sold as "100", and the years employed as "25". The weekly pay output should be "$783.30". But i end up getting $667.59 as the output. I cannot see what i am doing wrong.

Here are the guidelines that have to follow:

Full time representatives work 40 hours per week at a rate of $20.00 per hour Part time representatives work 20 hours per week at a rate of $10.00 per hour Some representatives belong to the union and pay $5.25 each week in union dues If the representative has worked 10 years or more they get a commission of 10% of sales, otherwise they get a commission of 5% of sales Widgets sell for $9.25 If a full time worker has sales that are more than 80% of their base pay they are entitled to a bonus of 5% of their sales All representatives pay a 16% FICA tax based on their total earnings

P.S. I know this is a lot of reading, but if you can help me with this, it would be like a Christmas miracle to me.

Answer 1

Your computation is off based on the union dues...
Apparently, to get the 783.30 pay, the union dues are deducted AFTER the FICA tax has been applied...

 800.00 (base) 
+ 46.25 (5% bonus when over 80% base) 
+ 92.50 (10% commission on 925 sales)
=======
 938.75
-150.20 (16% FICA)
=======
 788.55 Net pay before union dues
-  5.25 (union) 
=======
 783.30

private void btnDisplay_Click(object sender, EventArgs e)
{
   string EmploymentStatus = Convert.ToString(txtES.Text).ToLower();
   string UnionStatus = Convert.ToString(txtMS.Text).ToLower();
   double TotalSales = Convert.ToDouble(txtSales.Text) * 9.25;
   double Years = Convert.ToDouble(txtYears.Text);         
   double uniondues = 0;
   double FICA = 0;
   double bonus = 0;
   double WPay = 0;
   double TotalComission = 0;


   if (EmploymentStatus == "full")
   {
      WPay = 800.00;
      // since already in full-time status check, compute bonus here now.
      // based on 80% of base pay
      if (TotalSales > WPay * .80)
         bonus = TotalSales * .05;
   }
   else if (EmploymentStatus == "part")
      WPay = 200.00;
   else
      MessageBox.Show("Error, please enter either FULL or PART");

   // Only if qualified full/part time status
   if( WPay > 0 )
   {
      if (UnionStatus == "member")
         uniondues = 5.25;
      else if (UnionStatus == "non-member")
         uniondues = 0;
      else
         MessageBox.Show("Error, please enter either MEMBER or NON-MEMBER");

      if (Years >= 10)
         TotalComission = TotalSales * .10;
      else if (Years < 10)
         TotalComission = TotalSales * .05;
      else
         MessageBox.Show("Error, please enter a valid number");


      // NOW, build out the total pay before computing FICA
      WPay = WPay + bonus + TotalComission;

      // NOW Compute FICA
      FICA = WPay * .16;

      // and remove FICA and Union dues from gross pay to get net pay
      WPay = WPay - FICA - uniondues;
   }

   lblqWPay.Text = "The weekly pay for the employee is: " + (WPay.ToString("C"));
   lblqTS.Text = "The total sales for this employee is: " + (TotalSales.ToString("C"));
   lblqCom.Text = "The comission for this employee is: " + (TotalComission.ToString("C"));
   lblqBonus.Text = "The bonus for this employee is: " + (bonus.ToString("C"));
}

Answer 2

The value of 783.30 is wrong by my calculations. Doing the math by hand:

(800 (base) - 5.25 (union) + 92.5 (commision) + 46.25 (bonus))*.84 (tax) = 784.14. Unless the pay is determined differently from the guides you have mentioned your program is running correctly and the old one was wrong.