In a particular experiment at 300 , drops from 0.0225 to 0.00669 in 190 . The rate of disappearance of for this period is ________ .

a. 4.16×10^−5
b. 8.32×10^−5
c. 1.20×10^4
d. 1.66×10^−4
e. −1.54×10^−4