The firm's products are designed so that most customers can install them without any help. However, some customers do require support with installation. This support is provided 100% over the phone through a dedicated phone number and can range between 30 minutes and several hours, depending on the customer. To ensure that the firm gets feedback and other information from clients, a member of AEF's customer relations team "visits" with each client every quarter via Zoom (even if the customer did not make any purchases in the previous quarter). Most visits run around 30-35 minutes. The billing/payment processing activity takes the same amount of time regardless of the size or amount of the order placed. Since all products are roughly the same size, weight, and selling price, higher-revenue orders use more shipping resources than do lower- revenue orders. Based on this information, determine the hierarchy level for each cost pool and an appropriate allocation base for each pool. Note: Instead of product-level activities, AEF would have customer-level activities. Cost Pool Hierarchy Allocation Base Installation support Client feedback Billing Payment Processing Shipping