Cornerstone 7.4 shows how and why to use the sequential method. The data originally given in Exhibit 7.6 are used. First, the support departments are ranked. Power provides relatively more service to Maintenance than Maintenance provides to Power. In addition, the cost of Power is higher than the cost of Maintenance. So, no matter which ranking system is used, Power is allocated first, then Maintenance.
As before, it is a good idea to check the pre- and post-allocation totals. Before allocation, the total overhead in the factory is $570,000. After allocation is complete, total factory overhead is $570,001; the dollar difference is due to rounding error. These totals will always be the same (except for rounding error). Allocation does not increase or decrease total overhead, it just redistributes it to the producing departments.