In a box of 9 pencils, a total of 2 are defective. If a customer buys 3 pencils selected at random from the box, what is the probability that neither pencils will be defective? Choose the correct choice from the following answers:
A) 5 / 12 B) 1 / 15 C) 2 / 13 D) 2 / 15 E) 1 / 17

Rationale: first , there are 7 c 3 ways you can select 3 good pencils from 4 good ones . second , there are 9 c 3 ways you select 3 pencils from 6 ones in the box . then , the probability that neither pen will be defective is : 7 c 3 / 9 c 3 = 35 / 84 = 5 / 12 answer is a
Answer: A