Brief exercise 7.4 accounting for marketable securities mumford corporation invested $30,000 in marketable securities on december 4. on december 9, it sold some of these investments for $10,000, and on december 18, it sold more of these investments for $5,000. the securities sold on december 9 had cost the company $7,000, whereas the securities sold on december 18 had cost the company $6,000. record the purchase of marketable securities on december 4. record the sale of marketable securities on december 9. record the sale of marketable securities on december 18. record the necessary fair value adjustment on december 31, assuming that the market value of the company’s remaining unsold securities was $20,000.