The greatest common factor of 16 and the positive integer n is 4, and the greatest common factor of n and 45 is 3. Which of the following could be the greatest common factor of n and 420? Choose the correct choice:
A) 15
B) 48
C) 64
D) 84
E) 90
n includes the factors 2^2 (but not 2^3) and 3 (but not 3^2 or 5)   420 = 4*3*5*7   The GCF could be 12 or 84.   The answer is 84.
<result>D</result>
The greatest common factor of 16 and the positive integer n is 4, and the greatest common factor of n and 45 is 3. Which of the following could be the greatest common factor of n and 420?