我在数学上做错了什么

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"));

当我输入就业状态为"FULL"，工会状态为"MEMBER"时，销售数量为"100"，雇用年限为"25"。每周工资输出应为"783.30 美元"。但我最终得到 667.59 美元作为输出。我看不出我做错了什么。

以下是必须遵循的准则：

全职代表每周工作 40 小时，每小时 20.00 美元兼职代表每周工作 20 小时，费率为每小时 10.00 美元一些代表属于工会，每周支付5.25美元的工会会费如果代表工作了 10 年或更长时间，他们将获得销售额 10% 的佣金，否则他们将获得销售额 5% 的佣金小部件售价为9.25美元如果全职员工的销售额超过其基本工资的 80%，他们有权获得销售额的 5% 的奖金所有代表根据其总收入支付 16% 的 FICA 税

附言我知道这是很多阅读，但如果你能帮助我，这对我来说就像一个圣诞奇迹。

 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"));
}