Identifier is a name of variable, method, or class. There are rules for naming identifiers in Java. Based on those rules, explain which of the following identifiers are valid or invalid. If it not valid, explain the reason. Example: box: valid new: invalid, new is a reserve word. Answer: 1. name: 2. a+: 3. class: 4. Public: 5. 1st_name: 6. student id: