有如下Visual Basic程序: Private Sub Command1_Click(___) Dim a(1 To 100) As Integer, i As Integer, s As Integer s = 0 For i = 2 To 100 Step 2 a(i) = i * 2 s = s + a(i) Next i Text1.Text = Str(s) End Sub 问: (1)程序运行后,下标变量a(4)的值为_________。 (2)循环刚退出时,变量i的值为_________。