Find the difference. express the answer in scientific notation. (8.64 times 10 superscript 20 baseline) minus (7.83 times 10 superscript 20 baseline) 8.1 times 10 superscript 19 0.81 times 10 superscript 20 8.1 times 10 superscript 21 0.81 times 10 superscript 40