On May 5, 2020, Alexion Pharmaceuticals announced its acquisition of Portola Pharmaceuticals for $1.4 billion. On the same day, Alexion, Portola, and the S&P 500 index closed at $98.25, $17.85, and 2,868.44, respectively. Closing prices on May 4, 2020 were $103.84 for Alexion, $7.76 for Portola, and 2,842.74 for the S&P 500 index.

What is the announcement day abnormal return for Portola assuming its beta is 2.31? Please do not round numbers in intermediate steps. Write your final answer in decimal format to four decimal places (e.g., if abnormal return is 2.63%, write 0.0263).