In a box of 10 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 option:  A) 1 / 12  B) 7 / 15  C) 2 / 13  D) 2 / 15  E) 1 / 17

Rationale: "first , there are 8 c 3 ways you can select 3 good pencils from 4 good ones . second , there are 10 c 3 ways you select 3 pencils from 6 ones in the box . then , the probability that neither pen will be defective is : 8 c 3 / 10 c 3 = 56 / 120 = 7 / 15 answer is b"
Answer: B