During the synthesis stage of the cell cycle, a cell makes (replicates its own) DNA.
Economic profits equals total revenues minus the sum of explicit costs and implicit costs. Since explicit costs are already subtracted when arriving at the accounting profit, we can find economic profit by subtracting the implicit costs from the accounting profit.
Just because a business has zero economic profits does not mean that the business is not turning an accounting profit. In fact, a firm that produces zero economic profits produces an accounting profit, all else being equal. In the short run, some firms do not maintain zero economic profit. At this point, price is less than average total costs. According to Penn State University's Department of Energy and Mineral Development, in order for profit maximization of a firm to occur, implicit and explicit costs must equal total revenue.