What will be the value of dblSum after the button btnAdd is clicked, assuming that 25 is entered by the user into txtNum1, and 35 is entered into txtNum2?

```
Private Sub btnAdd_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles btnAdd.Click

Dim dblNum1, dblNum2, dblSum As Double
dblNum1 = CDbl(txtNum1.Text)
dblNum2 = CDbl(txtNum2.Text)
dblSum = Sum(dblNum1, dblNum2)
lblSum.Text = dblSum.ToString()

End Sub

Function Sum(ByVal dblNum1 As Double, ByVal dblNum2 As Double) as Double
Return dblNum1 + dblNum2
End Function
```

a. 60
b. 50
c. 0
d. 70

a. 60