Martinez, Inc., has tow separate departments (Human Resources and Building Maintenance) and two production departments (Machining and Assembly). The company allocates Building Maintenance cost on the basis of square footage and believes that Building Maintenance provides more service than Human Resources. The square footage occupied by each department follows: Human Resources 6,000 Building Maintenance 13,000 Machining 18,000 Assembly 26,000 Assuming use of the direct method, over how many square feet would the Building Maintenance cost be allocated (i.e., spread)