14-20 Customer profitability, service company. Instant Service (IS) repairs printers and photocopiers for five multisite companies in a tristate area. IS's costs consist of the cost of technicians and equipment that are directly traceable to the customer site and a pool of office overhead. Until recently, IS estimated customer profitability by allocating the office overhead to each customer based on share of revenues. For 2017, IS reported the following results: What is the customer profitability estimation method used by IS for 2017?
1) Allocating the office overhead to each customer based on share of revenues
2) Allocating the office overhead equally to all customers
3) Allocating the office overhead based on the number of technicians assigned to each customer
4) Allocating the office overhead based on the equipment used by each customer