学进去

（加试题）一个简单的四则混合运算式子（算式中只包含整数、+、-、*、/、=）的运算规则是先进行“*”或“/”，再进行“+”或“-”，下列是用 VB编写的简单四则混合运算的程序，运行程序时在文本框 Text1 中输入四则运算式子，单击命令按钮 Command1，在标签Label1 中输出结果。程序界面及代码如下。请回答以下问题。
(1) 若在文本框 Text1 中输入式子“12*5-32/4+20=”，则运行程序后在标签 Label1 中显示的内容是_________。

(2) 请在划线①②③处填入合适的代码，让程序能实现计算功能。
Private Sub Command1Click
Dim a(1 To 100) As Single, b(0 To 100) As String
Dim s As String, c As String   
Dim sz As Integer, i As Integer, k As Integer
s = Text1.Text:k = 0
For i = 1 To Len(s)

c = Mid(s, i, 1)

If c >= "0" And c <= "9" Then

sz = 0
Do While c >= "0" And c <= "9"
sz= ①________
i = i + 1
c = Mid(s, i, 1)
Loop
k = k + 1: a(k) = sz: b(k) = c
End If
Do While k > 1 And ②________
If b(k - 1) = "+" Then a(k - 1) = a(k - 1) + a(k)
If b(k - 1) = "-" Then a(k - 1) = a(k - 1) - a(k)
If b(k - 1) = "*" Then a(k - 1) = a(k - 1) * a(k)
If b(k - 1) = "/" Then a(k - 1) = a(k - 1) / a(k)
b(k-1) = b(k)
k = k - 1
Loop
Next i
Label1.Caption = "运算的结果是：" + Str(a(1))
End Sub
Function yxj(x As String) As Integer

If x = "*" Or x = "/" Then

yxj = 1

ElseIf x = "+" Or x = "-" Then

yxj = 2

Else

 ③________

End If

End Function