In shop there are 10 bulbs, a total of 4 are defective. If a customer buys 4 bulbs selected at random from the box, what is the probability that neither bulbs will be defective? Pick: A) 2 / 19 B) 3 / 29 C) 4 / 15 D) 1 / 15 E) 1 / 2

Rationale: first , there are 6 c 4 ways you can select 6 good bulbs from 4 good ones . second , there are 10 c 4 ways you select 4 bulbs from 10 ones in the box . then , the probability that neither bulb will be defective is : 6 c 4 / 10 c 4 = 15 / 210 = 1 / 15 answer is d
Answer: D