Public Function CalcEffectOfTransactionOnMargin(targdate As Date) As Decimal 'new 
     ' The code for this function is provided to you in a link from the homework.
     ' Make sure that you understand the financial logic.
     ' This function calculates the effect of the current transaction on your overall margin

     Select Case type
         Case "Sell"
             '  Sell has no effect on margin because you can only sell what you have long
             Return 0 ' effect of transaction on margin

         Case "Buy"
             If currentPositionInAP >= 0 Then
                 Return 0
             Else
                 If qty >= Math.Abs(currentPositionInAP) Then
                     Return -currentPositionInAP * mtm
                     ' buying eliminates all margin for this symbol
                 Else
                     Return (qty * mtm)
                     ' buying reduces the margin
                 End If
             End If

         Case "SellShort"
             Return -qty * mtm
             ' Selling short is easy: it always increases the margin

         Case "CashDiv"
             Return 0

         Case "X-Call"
             ' Two effects on margin: the change in options and the change in stocks
             Dim OptionEffect As Decimal = 0
             underlierCurrentPositionInAP = GetCurrentPositionInAP(underlier)

             ' first the effect of exercising the call on the call position
             If currentPositionInAP < 0 Then
                 OptionEffect = qty * mtm
                 ' i.e., it reduces the margin
             Else
                 OptionEffect = 0
             End If

             ' next, the effect of the called stock
             ' two cases: long and short calls.
             If currentPositionInAP >= 0 Then      ' long call is like buying
                 If underlierCurrentPositionInAP >= 0 Then
                     Return OptionEffect
                 Else
                     If qty >= Math.Abs(underlierCurrentPositionInAP) Then
                         Return OptionEffect - (underlierCurrentPositionInAP * mtmUnderlier)
                         ' X-call eliminates all margin for this symbol
                     Else
                         Return OptionEffect + (qty * mtmUnderlier)
                         ' X-call reduces the margin
                     End If
                 End If

             Else      '  exercising short calls is like selling

                 If underlierCurrentPositionInAP <= 0 Then
                     Return OptionEffect - (qty * mtmUnderlier)
                 Else   ' underlier positive
                     If underlierCurrentPositionInAP >= qty Then
                         Return OptionEffect
                     Else
                         Return OptionEffect - ((qty - underlierCurrentPositionInAP) * (qty * mtmUnderlier))
                     End If
                 End If
             End If

         Case "X-Put"
             ' Two effects on margin: the change in options and the change in stocks
             Dim OptionEffect As Decimal = 0
             underlierCurrentPositionInAP = GetCurrentPositionInAP(underlier)

             ' first the effect of exercising the option on the put position
             If currentPositionInAP < 0 Then
                 OptionEffect = qty * mtm
                 ' and it reduces the margin
             Else
                 OptionEffect = 0
             End If

             ' next, the effect of the stock
             ' two cases: long and short puts
             If currentPositionInAP < 0 Then      ' short put is like buying

                 If underlierCurrentPositionInAP >= 0 Then
                     Return OptionEffect
                 Else
                     If qty >= Math.Abs(underlierCurrentPositionInAP) Then
                         Return OptionEffect - (underlierCurrentPositionInAP * mtmUnderlier)
                         ' X-put eliminates all margin for this symbol
                     Else
                         Return OptionEffect + (qty * mtmUnderlier)
                         ' X-put reduces the margin
                     End If
                 End If

             Else      ' long put is like selling

                 If underlierCurrentPositionInAP <= 0 Then
                     Return OptionEffect - (qty * mtmUnderlier)
                 Else   ' underlier positive
                     If underlierCurrentPositionInAP >= qty Then
                         Return OptionEffect
                     Else
                         Return OptionEffect - ((qty - underlierCurrentPositionInAP) * mtmUnderlier)
                     End If
                 End If
             End If
     End Select
     MessageBox.Show("Holy BatApples! I could not figure out the impact of " + symbol + " on margin.  I returned $0.")
     Return 0
 End Function