public void AddContract(Contract contract)
        {
            Nanny  nanny  = GetNanny(contract.NannyId);
            Child  child  = GetChild(contract.ChildId);
            Mother mother = GetMother((child.MotherID));

            if (!BL_Tool.IsChildOver3Month(child))
            {
                throw new Exception("Child is too young...");
            }
            int ammountOfContracts = BL_Tool.GetNumberOfContractsByCondition(n => n.NannyId == nanny.ID);

            if (ammountOfContracts >= nanny.KidsCapacity)
            {
                throw new Exception("Nanny is full...");
            }
            if (!BL_Tool.CheckAgeIsInRange(nanny, child))
            {
                throw new Exception("Child's age is not within the nanny's age range...");
            }
            var contracts = GetContracts(c => c.ChildId == child.ID);

            foreach (var item in contracts)
            {
                if (BL_Tool.OverlappingTime(nanny, GetNanny(item.NannyId)))
                {
                    throw new Exception($"Warning:{child.Name} is already registered in those hours");
                }
            }
            contract.Signed = true;
            dal.AddContract(contract);
        }