#### Answer

The answer is below.

#### Work Step by Step

In order to write a number in scientific notation, we must use the form $ n \times 10^a$, where n is a number between 1 and 10 and a is the number of places the decimal of the original number has to be moved left to get the number n. (If the decimal is moved right, a is negative.) Using this gives:
a) $ 8.5 \times 10^4 $
b) $ 9 \times 10^{-4}$
c) $ 1.04 \times 10^{-6} $
d) $5.3 \times 10^7$