What is the greatest value of x such that 4^x is a factor of 21! ?	Choose the correct answer.
A) 5	B) 6	C) 3	D) 2	E) 4

Rationale: pretty simple , really . if m = 6 , then 4 m = 24 , which is 12 x 2 , both of which are included in 21 ! since 6 is the largest number here , its the answer . answer is b
Answer: B