Six pencils and two erasers cost $$3.20$$ dollars. One pencil costs $$40$$ cents. How much does one eraser cost? (Adapted from 2000 Math Kangaroo Problem, Level 3-4, Question \#5) 
选项为:A:$$20$$ cents  B:$$30$$ cents  C:$$40$$ cents  D:$$50$$ cents  E:$$60$$ cents  请回答其中一个选项.