A box contains ten bulbs out of which 6 are defective. If four bulbs are chosen at random, find the probability that all the four bulbs are defective?	Choose the correct choice from the following answers
A) 1/127	B) 1/210	C) 1/128	D) 1/198	E) 1/126
Out of nine, five are good and four are defective. Required probability   = 6C6/10C6   = 1/210   Answer: 1/210
<result>B</result>
A box contains ten bulbs out of which 6 are defective. If four bulbs are chosen at random, find the probability that all the four bulbs are defective?