Answer:
9.89×10^-9
Explanation:
0.000 000 009 89 = 9.89×10^-9
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We have introduced spaces in the number to make the digits easier to count. (Some technical publications will write the number with thin spaces for just that reason.) The most-significant digit is in the 9th place to the right of the decimal point, so has a place value of 10^-9.