Tannimen Square has 800 obsolete calculators in its inventory which have a cost of $16 each. If the calculators are reworked they could be sold for $23 each. If sold 'as-is', the revenue would be only $12 each. If Tannimen decides to rework the calculators, how much should the company be willing to invest to ensure that no additional loss occurs on the sale of the calculators?