In 2017, ABC company decided to switch from FIFO to the weighted-average inventory cost method. COGS reported under FIFO were 156 and 128 for 2015 and 2016 respectively. Under weighted-average COGS were 150 and 141 for 2015 and 2016 respectively. As presented in the 2017 financial statements, what will be the adjustment made to the 2016 beginning retained earnings balance?

A. (7)

B. 6

C. (19)

D. (13)