Owen buys electricity and food. The power company offers a volume discount: electricity costs $0.10 per kwh for the first 500 kwh, and $0.08 per kwh for electricity beyond 500 kwh. Suppose Owen's preferences have the declining MRS property, and that a unique bundle on the interior of Owen's budget line satisfies the tangency condition. Is that bundle necessarily a best choice? Explain your answer with a graph.