If n is the product of integers from 1 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) 10
B) 12
C) 15
D) 18
E) 20
Given: n=20!n=20!. The highest power k for which 2^k is a factor of n can be found with the above formula:   k=20/2+20/4+20/8+20/16=10+5+2+1= 
<gadget id="calculator">10+5+2+1</gadget>
<output>18</output>
18   Answer: 18.
<result>D</result>
If n is the product of integers from 1 to 20 inclusive what is the greatest integer k for which 2^k is a factor of n?