ANTLR 3 GRAMMAR : A Signed Even Number Grammar. Consider the following language description of a signed even number: A signed even number optionally has a “+” or “-“ to denote its sign followed by one more number of which the last number must be even. 

Task 1. Define the legal lexical tokens in the grammar for this language. You will likely want to define separate lexical rules for the numbers 0-9 as well as the even numbers. 

Task 2. Develop the parser rules for this grammar. As you develop/troubleshoot your grammar, be 
sure to utilize the Syntax Diagram to visualize the rules you are defining. 


this what I got so far but still out an error
NUMBER		:	'0'..'9';
EVEN_NUMBER	:	'0' | '2' | '4' | '6' | '8' ;


signedevennumber 	: ('+' | '-')? EVEN_NUMBER? NUMBER? NUMBER? EVEN_NUMBER;

ANY HELP PLEASE