AMC 10A 2018 Problem 7

Past Contests AMC 10 2018 Part A
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1

For how many (not necessarily positive) integer values of n is the value of 4000 \cdot\left(\dfrac{2}{5}\right)^{n} an integer?

Answer Choices
A. 3
B. 4
C. 6
D. 8
E. 9