martin and sons landscaping purchased shares of bcd stock at three different times

100 shares for 4300 on feb 1 2018

300 shares for 6900 on may 15 2019

200 shares for 10000 on jan 30 2020

on june 1 2021 they sold 265 shares and received gross proceeds of 13010. if they wanted to reduce the capital gain as much as possible which shares would they have had to specifically identity at the time of sale