Computing an Internal Rate of Return Dr. Whitten has decided to purchase equipment that has a cost of $60,000 and will produce a pretax net cash inflow of $30,000 per year over its estimated useful life of six years. The equipment will have no salvage value and will be depreciated by the straight-line method. The tax rate is 50 percent. Determine Dr. Whittens approximate after-tax internal rate of return.