GMAT Problem Solving Question 56: Decimals, exponents, and integers

 
Try the following GMAT Problem Solving question on how to turn a decimal product to a whole number.

Question 56:

What is the least integer value of $n$ for which the product $(0.004)(0.015)(0.0025)(10^n)$ is an integer ?

1. $\quad -10$

2. $\quad -8$

3. $\quad 0$

4. $\quad 8$

5. $\quad 10$