Sun Brite has a new pair of sunglasses it is evaluating. The company expects to sell 7,400 pairs of sunglasses at a price of $169 each and a variable cost of $121 each. The equipment necessary for the project will cost $385,000 and will be depreciated on a straight-line basis over the 7 -year life of the project. Fixed costs are $350,000 per year and the tax rate is 35 percent. How sensitive is the operating cash flow to a $1 increase in variable costs per pairs of sunglasses