Plz share with me the formula step by step with detailed explanations. Thank you a lot.

Winder, Knotter, and Nale is a small law firm that has 10 partners and 10 support people. The firm employs a job-order costing system to accumulate costs chargeable to each client, and it is organized into two departments-the Research and Documents Department and the Litigation Department. The firm uses predetermined overhead rates to charge the costs of these departments to its clients. At the beginning of the current year, the firm's management made the following estimates for the year: The predetermined overhead rate in the Research and Documents Department is based on research-hours, and the rate in the Litigation Department is based on direct lawyer cost. The costs charged to each client are made up of three elements: materials and supplies used, direct lawyer costs incurred, and an applied amount of overhead from each department in which work is performed on the case. Case 618-3 was initiated on February 10 and completed on June 30. During this period, the following costs and time were recorded on the case: Required: 1. Compute the predetermined overhead rate used during the year in the Research and Documents Department. Compute the rate used in the Litigation Department. 2. Using the rates you computed in (1) above, compute the total overhead cost applied to Case 618-3. 3. What is the total cost charged to Case 618-3? Show computations by department and in total for the case. 4. At the end of the year, the firm's records revealed the following actual cost and operating data for all cases handled during the year