visual studio 2010 showing Syntax error near ')' at y.ExecuteNonQuery code

Question

The following code snippet is for storing values in a table from grid view . And it is showing Unhandled SQLException at the line y.ExecuteNonQuery

the error is Syntax error near ')'

however i cannot determine what's wrong with the code. Help me out.

    private void button1_Click(object sender, EventArgs e)
    {
        string subtable = "";
        if (comboBox1.Text == "Physics")
        { subtable = "sub1"; }
        else if (comboBox1.Text == "Chemistry")
        { subtable = "sub2"; }
        else if (comboBox1.Text == "Maths")
        { subtable = "sub3"; }
        else
        { subtable = "sub4"; }

        x = new SqlConnection("Data Source= AHSUYA ;initial catalog=master;integrated security=sspi;");
        x.Open();
        for (int i = 0; i < dataGridView1.Rows.Count - 1; i++)
        {
            y = new SqlCommand("Insert into " + subtable + "values(@a,@b,@c)",x);
            y.Parameters.AddWithValue("@a", dateTimePicker1.Value.Date.ToShortDateString());
            y.Parameters.AddWithValue("@b", dataGridView1.Rows[i].Cells[0].Value.ToString());
            y.Parameters.AddWithValue("@c", dataGridView1.Rows[i].Cells[1].Value.ToString());   

            y.ExecuteNonQuery();
        }
        x.Close();

    }

`