When calculating cash flow, why is depreciation first subtracted but then added back in?a. Because it is not a real cash outflow but does create a tax deductible expenseb. Because it is an expense that can be immediately and fully deducted from the revenues of the firmc. Because it changes from negative to positive as the project moves forwardd. Because it serves to increase the amount of tax the firm will have to pay to the tax authoritiese. Because it has the unusual characteristic of switching signs in the middle of most projects