RULE 71. MEAL PERIOD.  (a) Engineers will be allowed 20 minutes for lunch between 4 1/2 and 6 hours after beginning work as a crew unit, without deduction in pay, the lunch period to be completed by the end of the sixth hour.  

(b) Engineers will not be required to work longer than 6 hours after first meal period without being allowed an additional 20 minutes for lunch, with no deduction in pay or time therefor.