Where does the 18/20 come from? To get the answer

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Gibbs Corporation owned 20,000 shares of Oliver Corporation's $5 par value common stock. These shares were purchased in 2007 for $180,000. On September 15, 2011 Gibbs declared a property dividend of one share of Oliver for everylten shares of Gibbs held by a stockholder. On that date, when the market price of Oliver was $14 per share there were 180,000 shares of Gibbs outstanding. What NET reduction in retained earnings would result from this property dividend