public void AddContract(Contract inputContract)
        {
            Nanny nanny = DalTools.GetNanny(inputContract.NannyID);
            Child child = DalTools.GetChild(inputContract.ChildID);

            //cheak if the age of the infant is under 3 month
            DateTime age = (DalTools.GetChild(inputContract.ChildID)).ChildAge;

            age.AddMonths(3);
            if (DateTime.Now < age)
            {
                throw new Exception("Can't add Child to Contract under 3 months");
            }

            //checks if nanny capacity is full
            if (nanny.IsNannyCapacityIsFull())
            {
                throw new Exception("Nanny hace reached the maximum infants capacity...");
            }

            //checks if child age is not over the maximum/minimum nanny accepts
            int childAgeInMonths = child.AgeInMonths();

            if (childAgeInMonths < nanny.NannyMinInfantAge || childAgeInMonths > nanny.NannyMaxInfantAge)
            {
                throw new Exception("Nanny can't accept this age");
            }

            if (inputContract.IsContractSigned)
            {
                //checks if contract salary calculated by month or by hour and updates the salary nanny
                if (inputContract.PaymentMethod == Payment_method.hourly)
                {
                    inputContract.HourlySalary = BlTools.CalculateHourlySalary(nanny, child);
                }
                else
                {
                    inputContract.MonthlySalary = BlTools.CalculateMonthlySalary(nanny, child);
                }
            }



            BlTools.GetChild(inputContract.ChildID).IsHaveNanny = true;
            dal.AddContract(inputContract);
        }