A and B are two multiples of 14, and Q is the set of consecutive integers between A and B, inclusive. If Q contains 11 multiples of 14, how many multiples of 7 are there in Q?
Pick:
A) 19
B) 20
C) 21
D) 22
E) 23

Rationale: "halfway between the multiples of 14 , there will be another multiple of 7 . the total number of multiples of 7 is 11 + 10 = 21 . the answer is c ."
Answer: C