I cannot figure out how they figured out overhead. Help

Lubricants, Inc., produces a special kind of grease that is widely used by race car drivers. The grease is produced in two processing departments: The following incomplete Work in Process account is available for the Refining Department for March: Work in ProcessRefining Department March 1 balance Materials Direct labor Overhead 31,600 155,600 64,200 475,000 March 31 balance ? Completed and transferred to Blending ? The March 1 work in process inventory in the Refining Department consists of the following elements: materials, $7,100; direct labor, $4,600; and overhead, $19,900. Costs incurred during March in the Blending Department were: materials used, $45,000; direct labor, $16,400; and overhead cost applied to production, $110,000. Required: 1. Prepare journal entries to record the costs incurred in both the Refining Department and Blending Department during March. (If no entry is required for a transaction/event, select "No journal entry required" in the first account field.) a. Raw materials were issued for use in production. b. Direct labor costs were incurred. c. Manufacturing overhead costs for the entire factory were incurred, $656,000. (Credit Accounts Payable.) d. Manufacturing overhead cost was applied to production using a predetermined overhead rate. e. Units that were complete with respect to processing in the Refining Department were transferred to the Blending Department, $622,000. f. Units that were complete with respect to processing in the Blending Department were transferred to Finished Goods, $730,000. g. Completed units were sold on account, $1,380,000. The Cost of Goods Sold was $650,000. Post the journal entries from (1) above to T-accounts. The following account balances existed at the beginning of March. (The beginning balance in the Refining Department's Work in Process account is given on the prior page.) Raw materials Work in processBlending Department Finished goods $205,600 $ 47,000 $ 14,000 After posting the entries to the T-accounts, find the ending balance in the inventory accounts and the manufacturing overhead account