The decrease in selling general and administrative expenses primarily reflects the following 162 million decrease in professional service expenses primarily due to a decrease in reliance on thirdparty selling general and administrative contractors as well as a transaction fee for the Roche transaction incurred during the six months ended June 30 2020 with no similar activity incurred during the six months ended June 30 2021 and 22 million increase in stockbased compensation primarily due to changes in stock price