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 140? Choose the correct choice from the following choices:
A) 3  B) 6  C) 28  D) 42  E) 70
n includes the factors 2^2 (but not 2^3) and 3 (but not 3^2 or 5)   140 = 4*5*7   The G28F could be 4 or 28   The answer is 28.
<result>C</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 140?