Can anyone explain this question to me step by step. Thanks!

John?s Butter and Egg Business is such that he pays an effective tax rate of 40%. John is considering the purchase of a new Turbo Churn for $40,000. This churn is a special handling device for food manufacture and has an estimated life of 4 years and a salvage value of $5,000. The new churn is expected to generate an addition gross income of $15,000 for each of the 4 years of use. If John works with an after- tax MARR of 14%, and use DDB depreciation, help him to decide if he should buy the churn with federal tax consideration. The DDB depreciation schedule. Find before-tax cash flows (BTCF) and after-tax cash flows (ATCF). Should he buy the churn and why