RULE 10. MONTHLY GUARANTEE.    (a) Regularly assigned passenger conductors and brakemen who are ready for service the entire month and who do not lay off of their own accord shall receive the monthly guarantee provided for in Rule 1, exclusive of overtime except that former higher monthly guarantees shall be preserved. Extra service may be required sufficient to make up these guarantees, and may be made between regular trips; may be made on lay-off days; or may be made before or after completion of the trip. If extra service is made between trips which go to make up a day's assignment, such extra service will be paid for on the basis of miles or hours, whichever is the greater, with a minimum of one hour. Extra service before or after the completion of a day's work will pay not less than the minimum day. The basis of pay for extra service apply only in making up the guarantees. After guarantees are absorbed schedule provisions for extra service apply.  

     (b) When a regularly assigned passenger man lays off of his own accord or is held out of service, the extra man will receive the same compensation the regular man would have received, and the amount paid the extra man, or men, will be deducted from the amount the regular man would have received had he remained in service, the sum of the payments to the man, or men, who may be used on the run equaling the monthly guarantee.