Lincoln Corporation buys and sells widgets and uses a periodic system for accounting purposes. According to counts that were taken, the company started the year with 4,000 units and ended the year with 5,000. However, during the period, an additional 17,000 widgets were acquired. All inventory items are bought by the company for $7 each, a figure that includes all normal and necessary costs. What was the number of units sold for this period? a) 16,000 b) 26,000 c) 8,000 d) 17,000