DataSource Controls :: Save Values In GridView With 2 Tables

I have a form with several DropDownlists and TextBoxes, Each dropdownlist depends on the selection of the previouse one.. and there is a submit button. Once the user clicks on it, information entered by the user is displayed in a GridView and saved as well in the database. The GridView holdes information from two tables I used joining) , but once I click on the Submit button I receive this error: Arithmetic overflow error converting varchar to data type numeric. The statement has been terminated. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Data.SqlClient.SqlException: Arithmetic overflow error converting varchar to data type numeric. The statement has been terminated. Source Error:

[Code]....

Imports System.Data.SqlClient
Imports System.Web.Configuration
Partial
Class Members_MembersCalculator
Inherits System.Web.UI.Page
Protected Sub CalculateButton_Click(ByVal sender
As Object,
ByVal e As System.EventArgs)
Handles CalculateButton.Click
Dim objConnection As SqlConnection
Dim objDataCommand As SqlCommand
Dim c_manu, c_model, c_date
As String
Dim sSQL As
String
Dim ConnectionString As
String
Dim c_factor As
Double
Dim c_result
As Double
Dim c_milage As
Double
Dim c_id As
Integer
Dim c_year As
Integer
c_manu = ManDropDownList.Text
c_year = YearDropDownList.Text
c_model = ModelDropDownList.Text
c_milage = MilageTextBox.Text
c_factor = FactorDropDownList.Text
c_id = CarIDDropDownList.Text
c_date = CarDateTextBox.Text
c_result = c_factor * c_milage
ConnectionString = WebConfigurationManager.ConnectionStrings("Carbon_free_ConnectionString").ConnectionString
objConnection = New SqlConnection(ConnectionString)
objConnection.Open()
sSQL = "Insert into car (Manufacture, year, Model, car_factor)" & _
"values('" & c_manu &
" ', ' " & c_year & " ',' " & c_model &
" ', ' " & c_factor &
" ')"
objDataCommand = New SqlCommand(sSQL, objConnection)
objDataCommand.ExecuteNonQuery()
objConnection.Close()
objConnection = New SqlConnection(ConnectionString)
objConnection.Open()
sSQL = "Insert into car_Result (car_id, car_Result_Date, Car_result)" & _
"values('" & c_id &
" ', ' " & c_date & " ',' " & c_result &
" ')"
objDataCommand = New SqlCommand(sSQL, objConnection)
objDataCommand.ExecuteNonQuery()
objConnection.Close()
msgLabel.Text = "Your records have been calculated successfuly, Thank you."
'CarDateTextBox.Text = ""
'MilageTextBox.Text = ""
CarGridSqlDataSource.DataBind()
CarGridView.DataBind()
End Sub
End
Class