step by step formula not excel

Consider a four-year project with the following information: initial fixed asset investment = $620,000, straight-line depreciation to zero over the four-year life, zero salvage value, price = $43, variable costs = $35: fixed costs = $210,000, quantity sold = 100,000 units; tax rate = 34% Using the new level of quantity 80,000. How sensitive is OCF to changes in quantity sold? (Do not round intermediate calculations. Round the final answer to 2