4. High-End Fashions, Inc., bought a production line of ankle-length skirts last year at a cost of $500,000. This year, however, miniskirts are hot in the market and ankle-length skirts are completely out of fashion. High-End has the option to rebuild the production line and use it to produce miniskirts with a cost of $300,000 and expected revenue of $700,000. How should the company treat the cost of $500,000 of the old production line in evaluating the rebuilding plan?