If n is the product of all the integers from 5 to 20, inclusive, what is the greatest integer k for which 2^k is a factor of n ?
Choose the correct choice from the following:
A) 11
B) 12
C) 13
D) 14
E) 15
20/2= 
<gadget id="calculator">20/2</gadget>
<output>10</output>
10   10/2= 
<gadget id="calculator">10/2</gadget>
<output>5</output>
5   Ans: 10+5= 
<gadget id="calculator"> 10+5</gadget>
<output>15</output>
15   ANSW15R:15
<result>E</result>
If n is the product of all the integers from 5 to 20, inclusive, what is the greatest integer k for which 2^k is a factor of n ?