A fair 2 sided coin is flipped 4 times. What is the probability that tails will be the result at least twice, but not more than 4 times?  Answers
A) 1 / 8	B) 2 / 3	C) 5 / 8	D) 4 / 7	E) 3 / 7

Rationale: "at least twice , but not more than 4 timesmeans exactly 2 times , 3 times , 4 times the probability of getting exactly k results out of n flips is nck / 2 ^ n 4 c 2 / 2 ^ 4 + 4 c 3 / 2 ^ 4 = 10 / 16 = 5 / 8 option : c"
Answer: C