add two decimal and add confirm dialog if press back button

lib/pages/rates/shipment_rates_calculate.dart

@@ -2,6 +2,7 @@ import 'package:fcs/domain/entities/carton.dart';
 import 'package:fcs/domain/entities/cargo_type.dart';
 import 'package:fcs/domain/entities/rate.dart';
 import 'package:fcs/helpers/theme.dart';
+import 'package:fcs/pages/main/util.dart';
 import 'package:fcs/pages/rates/model/shipment_rate_model.dart';
 import 'package:fcs/pages/widgets/display_text.dart';
 import 'package:fcs/pages/widgets/input_text.dart';
@@ -46,7 +47,7 @@ class _ShipmentRatesCalState extends State<ShipmentRatesCal> {
     _lengthController.text = '12';
     _widthController.text = '12';
     _heightController.text = '12';
-    _actualWeightCtl.text = "10";
+    _actualWeightCtl.text = "10.00";
     _calShipmentWeight();
   }
 
@@ -141,7 +142,11 @@ class _ShipmentRatesCalState extends State<ShipmentRatesCal> {
           centerTitle: true,
           leading: new IconButton(
             icon: new Icon(CupertinoIcons.back, color: primaryColor),
-            onPressed: () => Navigator.of(context).pop(),
+            onPressed: () {
+              showConfirmDialog(context, "back.button_confirm", () {
+                Navigator.of(context).pop();
+              });
+            },
           ),
           backgroundColor: Colors.white,
           shadowColor: Colors.transparent,
@@ -163,7 +168,7 @@ class _ShipmentRatesCalState extends State<ShipmentRatesCal> {
                   LocalText(context, "rate.delivery_fee",
                       color: primaryColor, fontSize: 16),
                   Text(
-                    ':\$ $_deliveryFee',
+                    ':\$ ${_deliveryFee.toStringAsFixed(2)}',
                     style: TextStyle(
                       color: primaryColor,
                       fontSize: 16,