When calculating city delivery cost, we include the entire (fixed and volume variable) in-office and out-of-office cost24 for all city routes, plus the cost of overtime, supervision, space, and vehicles.
To calculate city delivery cost, we only need to know the cost of overtime. 
mnli hypothesis: To calculate city delivery cost, we only need to know the cost of overtime.  premise: When calculating city delivery cost, we include the entire (fixed and volume variable) in-office and out-of-office cost24 for all city routes, plus the cost of overtime, supervision, space, and vehicles.