Penny owns 540 shares of Mack Co. They have an adjusted cost base of $15.43 per share. On March 31, 2020, Penny sold all of her shares for $12.89 per share. After she sold the shares, the price fell further and on April 15, 2020, Penny purchased 260 of the same class of shares of Mack Co. for $11.91 per share. She was still holding all of the shares at the end of 2020. What is the adjusted cost base of the Mack Co shares Penny holds at the end of 2020?