In ASP.NET MVC C# database First I am doing sum of values in textboxes but in database it does not insert the SUM result

I want to find sum of values in textboxes and then display the SUM in another textbox and also STORE THE SUM IN DATABASE . Using the code below it succesfully find sum and display it in another textbox However it does not store the sum in database.

I checked the database, it shows the value NULL is entered in TotalAvgHours field of database.

[HttpPost]
            [ValidateAntiForgeryToken]
            public ActionResult Create(TimePeriodViewModel timePeriodVM)
            {
                var timeperiod = new TimePeriod
                {
                 
                    TotalAvgHours = timePeriodVM.TimePeriod.TotalAvgHours,
                    
    }

View

            <td>
        @Html.TextBox("TotalAvgHours", "", "{0:c}", new { disabled = "disabled", @class = "form-control", id = "res2" })
        <script type="text/javascript">

            function sum2() {
                var one = document.getElementById('a2').value || "0";
                var two = document.getElementById('b2').value || "0";
                var three = document.getElementById('c2').value || "0";
                var four = document.getElementById('d2').value || "0";
                var five = document.getElementById('e2').value || "0";
                var six = document.getElementById('f2').value || "0";
                var seven = document.getElementById('g2').value || "0";
                var eight = document.getElementById('h2').value || "0";
                var nine = document.getElementById('i2').value || "0";
                var ten = document.getElementById('j2').value || "0";
                var eleven = document.getElementById('k2').value || "0";
                var twelve = document.getElementById('l2').value || "0";
                var thirteen = document.getElementById('m2').value || "0";
                var fourteen = document.getElementById('n2').value || "0";
                var fifteen = document.getElementById('o2').value || "0";

                var result = parseFloat(one) + parseFloat(two) + parseFloat(three) + parseFloat(four) + parseFloat(five) + parseFloat(six) + parseFloat(seven) +
                    parseFloat(eight) + parseFloat(nine) + parseFloat(ten) + parseFloat(eleven) + parseFloat(twelve) + parseFloat(thirteen) + parseFloat(fourteen) + parseFloat(fifteen);
                if (!isNaN(result)) {
                    document.getElementById('res2').value = result;
                }
            }
            window.onload = sum2;

        </script>
    </td>
    
    
</tr>

TimePeriodViewModel

 public class TimePeriodViewModel
    {
        public IEnumerable<Personnel> Personnels { get; set; }
       //public Personnel Personnel { get; set; }
       public int PersonnelID { get; set; }
       
        public IEnumerable<DailyRegister> DailyRegisters { get; set; }
        public DailyRegister DailyRegister { get; set; }
        public TimePeriod TimePeriod { get; set; }

    }

TimePeriod

 public partial class TimePeriod
    {
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
        public TimePeriod()
        {
            this.DailyRegisters = new HashSet<DailyRegister>();
        }
    
        public int TimePeriodID { get; set; }
        public int PersonnelID { get; set; }
        public System.DateTime StartDate { get; set; }
        public System.DateTime EndDate { get; set; }
        public Nullable<bool> IsSignedAvgAgreement { get; set; }
        public Nullable<bool> IsSignedTimeSheet { get; set; }
        public string SignedAvgBy { get; set; }
        public string SignedTimeSheetBy { get; set; }
        public Nullable<System.DateTime> SignedTimeSheetDate { get; set; }
        public Nullable<decimal> TotalAvgHours { get; set; }
        public Nullable<decimal> TotalTimeSheetHours { get; set; }
        public Nullable<decimal> TotalOvertime { get; set; }
}