completed assignment

force-app/main/default/triggers/ValidNumber.trigger

@@ -0,0 +1,14 @@
+trigger ValidNumber on Contact (before insert) 
+{
+    String phonePattern = '(123) 456-7890';
+    
+    for (Contact contact : Trigger.New)
+    {
+        
+        if (!Pattern.matches(phonePattern, contact.Phone))
+        {
+            
+            contact.Phone.addError('Invalid phone format!');
+        }
+    }
+}