An investor purchased shares of XYZ Company as follows: 300 in year 1 at $25.50/share, 700 in year 2 at $22.25, and 600 in year 3 at $27.00. He sold 1000 shares in year 4 @ $45.25/share. Calculate his adjusted cost base at the time of sale. a. $24.50 b. $24.64 c. $25.50 d. $23.28