Required information [The following information applies to the questions displayed below.] Trey Monson starts a merchandising business on December 1 and enters into the following three inventory purchases. Monson uses a perpetual inventory system. Also, on December 15, Monson sells 15 units for $31 each. Purchases on December 7 Purchases on December 14 Purchases on December 21 10 units @ $17.00 cost 20 units @ $23.00 cost 15 units @ $25.00 cost