Visual Basic.NET - Multiplicar letras

Public Class Form1

    Dim c1, C2, C3, C4 As Integer

    Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged

        Dim num = (From letra In TextBox1.Text Where letra = "P").Count

        C1 = num

        TextBox5.Text = (c1 + C2 + C3 + C4) * 3000

    End Sub

    Private Sub TextBox2_TextChanged(sender As Object, e As EventArgs) Handles TextBox2.TextChanged

        Dim num = (From letra In TextBox2.Text Where letra = "P").Count

        C2 = num

        TextBox5.Text = (c1 + C2 + C3 + C4) * 3000

    End Sub

    Private Sub TextBox3_TextChanged(sender As Object, e As EventArgs) Handles TextBox3.TextChanged

        Dim num = (From letra In TextBox3.Text Where letra = "P").Count

        C3 = num

        TextBox5.Text = (c1 + C2 + C3 + C4) * 3000

    End Sub

    Private Sub TextBox4_TextChanged(sender As Object, e As EventArgs) Handles TextBox4.TextChanged

        Dim num = (From letra In TextBox4.Text Where letra = "P").Count

        C4 = num

        TextBox5.Text = (c1 + C2 + C3 + C4) * 3000

    End Sub

End Class